Merge #5144

5144: Exactly 512 bytes docid fails r=Kerollmops a=dureuill

# Pull Request

## Related issue
Fixes #5050 

## What does this PR do?
- Return a user error rather than an internal one for docids of exactly 512 bytes
- Fix up error message to indicate that exactly 512 bytes long docids are not supported.
- Fix up error message to reflect that index uids are actually limited to 400 bytes in length

## Impact

- Impacts docs: 
    - update [this paragraph](https://www.meilisearch.com/docs/learn/resources/known_limitations#length-of-primary-key-values) to say 511 bytes instead of 512 

Co-authored-by: Louis Dureuil <louis@meilisearch.com>

crates/index-scheduler/src/error.rs

@@ -1,12 +1,13 @@
 use std::fmt::Display;
 
-use crate::TaskId;
 use meilisearch_types::batches::BatchId;
 use meilisearch_types::error::{Code, ErrorCode};
 use meilisearch_types::tasks::{Kind, Status};
 use meilisearch_types::{heed, milli};
 use thiserror::Error;
 
+use crate::TaskId;
+
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum DateField {
     BeforeEnqueuedAt,
@@ -103,7 +104,7 @@ pub enum Error {
     )]
     InvalidTaskCanceledBy { canceled_by: String },
     #[error(
-        "{index_uid} is not a valid index uid. Index uid can be an integer or a string containing only alphanumeric characters, hyphens (-) and underscores (_), and can not be more than 512 bytes."
+        "{index_uid} is not a valid index uid. Index uid can be an integer or a string containing only alphanumeric characters, hyphens (-) and underscores (_), and can not be more than 400 bytes."
     )]
     InvalidIndexUid { index_uid: String },
     #[error("Task `{0}` not found.")]