Move index swap error handling from meilisearch-http to index-scheduler

And make index_not_found error asynchronous, since we can't know
whether the index will exist by the time the index swap task is
processed.

Improve the index-swap test to verify that future tasks are not swapped
and to test the new error messages that were introduced.

index-scheduler/src/snapshots/lib.rs/swap_indexes/first_swap_processed.snap

@@ -11,19 +11,20 @@ source: index-scheduler/src/lib.rs
 2 {uid: 2, status: succeeded, details: { primary_key: Some("id") }, kind: IndexCreation { index_uid: "d", primary_key: Some("id") }}
 3 {uid: 3, status: succeeded, details: { primary_key: Some("id") }, kind: IndexCreation { index_uid: "c", primary_key: Some("id") }}
 4 {uid: 4, status: succeeded, details: { swaps: [IndexSwap { indexes: ("a", "b") }, IndexSwap { indexes: ("c", "d") }] }, kind: IndexSwap { swaps: [IndexSwap { indexes: ("a", "b") }, IndexSwap { indexes: ("c", "d") }] }}
+5 {uid: 5, status: enqueued, details: { swaps: [IndexSwap { indexes: ("a", "c") }] }, kind: IndexSwap { swaps: [IndexSwap { indexes: ("a", "c") }] }}
 ----------------------------------------------------------------------
 ### Status:
-enqueued []
+enqueued [5,]
 succeeded [0,1,2,3,4,]
 ----------------------------------------------------------------------
 ### Kind:
 "indexCreation" [0,1,2,3,]
-"indexSwap" [4,]
+"indexSwap" [4,5,]
 ----------------------------------------------------------------------
 ### Index Tasks:
-a [1,4,]
+a [1,4,5,]
 b [0,4,]
-c [3,4,]
+c [3,4,5,]
 d [2,4,]
 ----------------------------------------------------------------------
 ### Index Mapper:
@@ -35,6 +36,7 @@ d [2,4,]
 [timestamp] [2,]
 [timestamp] [3,]
 [timestamp] [4,]
+[timestamp] [5,]
 ----------------------------------------------------------------------
 ### Started At:
 [timestamp] [0,]

index-scheduler/src/snapshots/lib.rs/swap_indexes/two_swaps_registered.snap

@@ -0,0 +1,56 @@
+---
+source: index-scheduler/src/lib.rs
+---
+### Autobatching Enabled = true
+### Processing Tasks:
+[]
+----------------------------------------------------------------------
+### All Tasks:
+0 {uid: 0, status: succeeded, details: { primary_key: Some("id") }, kind: IndexCreation { index_uid: "a", primary_key: Some("id") }}
+1 {uid: 1, status: succeeded, details: { primary_key: Some("id") }, kind: IndexCreation { index_uid: "b", primary_key: Some("id") }}
+2 {uid: 2, status: succeeded, details: { primary_key: Some("id") }, kind: IndexCreation { index_uid: "c", primary_key: Some("id") }}
+3 {uid: 3, status: succeeded, details: { primary_key: Some("id") }, kind: IndexCreation { index_uid: "d", primary_key: Some("id") }}
+4 {uid: 4, status: enqueued, details: { swaps: [IndexSwap { indexes: ("a", "b") }, IndexSwap { indexes: ("c", "d") }] }, kind: IndexSwap { swaps: [IndexSwap { indexes: ("a", "b") }, IndexSwap { indexes: ("c", "d") }] }}
+5 {uid: 5, status: enqueued, details: { swaps: [IndexSwap { indexes: ("a", "c") }] }, kind: IndexSwap { swaps: [IndexSwap { indexes: ("a", "c") }] }}
+----------------------------------------------------------------------
+### Status:
+enqueued [4,5,]
+succeeded [0,1,2,3,]
+----------------------------------------------------------------------
+### Kind:
+"indexCreation" [0,1,2,3,]
+"indexSwap" [4,5,]
+----------------------------------------------------------------------
+### Index Tasks:
+a [0,4,5,]
+b [1,4,]
+c [2,4,5,]
+d [3,4,]
+----------------------------------------------------------------------
+### Index Mapper:
+["a", "b", "c", "d"]
+----------------------------------------------------------------------
+### Enqueued At:
+[timestamp] [0,]
+[timestamp] [1,]
+[timestamp] [2,]
+[timestamp] [3,]
+[timestamp] [4,]
+[timestamp] [5,]
+----------------------------------------------------------------------
+### Started At:
+[timestamp] [0,]
+[timestamp] [1,]
+[timestamp] [2,]
+[timestamp] [3,]
+----------------------------------------------------------------------
+### Finished At:
+[timestamp] [0,]
+[timestamp] [1,]
+[timestamp] [2,]
+[timestamp] [3,]
+----------------------------------------------------------------------
+### File Store:
+
+----------------------------------------------------------------------
+

index-scheduler/src/snapshots/lib.rs/swap_indexes_errors/first_swap_failed.snap

@@ -0,0 +1,59 @@
+---
+source: index-scheduler/src/lib.rs
+---
+### Autobatching Enabled = true
+### Processing Tasks:
+[]
+----------------------------------------------------------------------
+### All Tasks:
+0 {uid: 0, status: succeeded, details: { primary_key: Some("id") }, kind: IndexCreation { index_uid: "a", primary_key: Some("id") }}
+1 {uid: 1, status: succeeded, details: { primary_key: Some("id") }, kind: IndexCreation { index_uid: "b", primary_key: Some("id") }}
+2 {uid: 2, status: succeeded, details: { primary_key: Some("id") }, kind: IndexCreation { index_uid: "c", primary_key: Some("id") }}
+3 {uid: 3, status: succeeded, details: { primary_key: Some("id") }, kind: IndexCreation { index_uid: "d", primary_key: Some("id") }}
+4 {uid: 4, status: failed, error: ResponseError { code: 200, message: "Indexes `e`, `f` not found.", error_code: "index_not_found", error_type: "invalid_request", error_link: "https://docs.meilisearch.com/errors#index_not_found" }, details: { swaps: [IndexSwap { indexes: ("a", "b") }, IndexSwap { indexes: ("c", "e") }, IndexSwap { indexes: ("d", "f") }] }, kind: IndexSwap { swaps: [IndexSwap { indexes: ("a", "b") }, IndexSwap { indexes: ("c", "e") }, IndexSwap { indexes: ("d", "f") }] }}
+----------------------------------------------------------------------
+### Status:
+enqueued []
+succeeded [0,1,2,3,]
+failed [4,]
+----------------------------------------------------------------------
+### Kind:
+"indexCreation" [0,1,2,3,]
+"indexSwap" [4,]
+----------------------------------------------------------------------
+### Index Tasks:
+a [0,4,]
+b [1,4,]
+c [2,4,]
+d [3,4,]
+e [4,]
+f [4,]
+----------------------------------------------------------------------
+### Index Mapper:
+["a", "b", "c", "d"]
+----------------------------------------------------------------------
+### Enqueued At:
+[timestamp] [0,]
+[timestamp] [1,]
+[timestamp] [2,]
+[timestamp] [3,]
+[timestamp] [4,]
+----------------------------------------------------------------------
+### Started At:
+[timestamp] [0,]
+[timestamp] [1,]
+[timestamp] [2,]
+[timestamp] [3,]
+[timestamp] [4,]
+----------------------------------------------------------------------
+### Finished At:
+[timestamp] [0,]
+[timestamp] [1,]
+[timestamp] [2,]
+[timestamp] [3,]
+[timestamp] [4,]
+----------------------------------------------------------------------
+### File Store:
+
+----------------------------------------------------------------------
+

index-scheduler/src/snapshots/lib.rs/swap_indexes_errors/initial_tasks_processed.snap

@@ -0,0 +1,51 @@
+---
+source: index-scheduler/src/lib.rs
+---
+### Autobatching Enabled = true
+### Processing Tasks:
+[]
+----------------------------------------------------------------------
+### All Tasks:
+0 {uid: 0, status: succeeded, details: { primary_key: Some("id") }, kind: IndexCreation { index_uid: "a", primary_key: Some("id") }}
+1 {uid: 1, status: succeeded, details: { primary_key: Some("id") }, kind: IndexCreation { index_uid: "b", primary_key: Some("id") }}
+2 {uid: 2, status: succeeded, details: { primary_key: Some("id") }, kind: IndexCreation { index_uid: "c", primary_key: Some("id") }}
+3 {uid: 3, status: succeeded, details: { primary_key: Some("id") }, kind: IndexCreation { index_uid: "d", primary_key: Some("id") }}
+----------------------------------------------------------------------
+### Status:
+enqueued []
+succeeded [0,1,2,3,]
+----------------------------------------------------------------------
+### Kind:
+"indexCreation" [0,1,2,3,]
+----------------------------------------------------------------------
+### Index Tasks:
+a [0,]
+b [1,]
+c [2,]
+d [3,]
+----------------------------------------------------------------------
+### Index Mapper:
+["a", "b", "c", "d"]
+----------------------------------------------------------------------
+### Enqueued At:
+[timestamp] [0,]
+[timestamp] [1,]
+[timestamp] [2,]
+[timestamp] [3,]
+----------------------------------------------------------------------
+### Started At:
+[timestamp] [0,]
+[timestamp] [1,]
+[timestamp] [2,]
+[timestamp] [3,]
+----------------------------------------------------------------------
+### Finished At:
+[timestamp] [0,]
+[timestamp] [1,]
+[timestamp] [2,]
+[timestamp] [3,]
+----------------------------------------------------------------------
+### File Store:
+
+----------------------------------------------------------------------
+