Implemented Ollama as an embeddings provider

Initial prototype of Ollama embeddings actually working, error handlign / retries still missing.

Allow model to be any String and require dimensions parameter

Fixed rustfmt formatting issues

There were some formatting issues in the initial PR and this should not make the changes comply with the Rust style guidelines

Because I accidentally didn't follow the style guide for commits in my commit messages I squashed them into one to comply

milli/src/vector/openai.rs

@@ -429,12 +429,12 @@ impl Embedder {
 
 // retrying in case of failure
 
-struct Retry {
-    error: EmbedError,
+pub struct Retry {
+    pub error: EmbedError,
     strategy: RetryStrategy,
 }
 
-enum RetryStrategy {
+pub enum RetryStrategy {
     GiveUp,
     Retry,
     RetryTokenized,
@@ -442,23 +442,23 @@ enum RetryStrategy {
 }
 
 impl Retry {
-    fn give_up(error: EmbedError) -> Self {
+    pub fn give_up(error: EmbedError) -> Self {
         Self { error, strategy: RetryStrategy::GiveUp }
     }
 
-    fn retry_later(error: EmbedError) -> Self {
+    pub fn retry_later(error: EmbedError) -> Self {
         Self { error, strategy: RetryStrategy::Retry }
     }
 
-    fn retry_tokenized(error: EmbedError) -> Self {
+    pub fn retry_tokenized(error: EmbedError) -> Self {
         Self { error, strategy: RetryStrategy::RetryTokenized }
     }
 
-    fn rate_limited(error: EmbedError) -> Self {
+    pub fn rate_limited(error: EmbedError) -> Self {
         Self { error, strategy: RetryStrategy::RetryAfterRateLimit }
     }
 
-    fn into_duration(self, attempt: u32) -> Result<tokio::time::Duration, EmbedError> {
+    pub fn into_duration(self, attempt: u32) -> Result<tokio::time::Duration, EmbedError> {
         match self.strategy {
             RetryStrategy::GiveUp => Err(self.error),
             RetryStrategy::Retry => Ok(tokio::time::Duration::from_millis((10u64).pow(attempt))),
@@ -469,11 +469,11 @@ impl Retry {
         }
     }
 
-    fn must_tokenize(&self) -> bool {
+    pub fn must_tokenize(&self) -> bool {
         matches!(self.strategy, RetryStrategy::RetryTokenized)
     }
 
-    fn into_error(self) -> EmbedError {
+    pub fn into_error(self) -> EmbedError {
         self.error
     }
 }