Update Inference specification for Mistral's completion and chat completion tasks (#4464)

* Enhance Mistral integration: update model documentation and expand task types

* Enhance Mistral integration: update task types and improve documentation

* Update json schema

---------

Co-authored-by: Quentin Pradet <quentin.pradet@elastic.co>

Author: Jan-Kazlouski-elastic

output/openapi/elasticsearch-openapi.json

@@ -999,7 +999,7 @@ export class MistralServiceSettings {
   max_input_tokens?: integer
   /**
    * The name of the model to use for the inference task.
-   * Refer to the Mistral models documentation for the list of available text embedding models.
+   * Refer to the Mistral models documentation for the list of available models.
    * @ext_doc_id mistral-api-models
    */
   model: string
@@ -1011,7 +1011,9 @@ export class MistralServiceSettings {
 }
 
 export enum MistralTaskType {
-  text_embedding
+  text_embedding,
+  completion,
+  chat_completion
 }
 
 export enum MistralServiceType {

output/openapi/elasticsearch-serverless-openapi.json

@@ -90,7 +90,9 @@ export enum TaskTypeHuggingFace {
 }
 
 export enum TaskTypeMistral {
-  text_embedding
+  text_embedding,
+  chat_completion,
+  completion
 }
 
 export enum TaskTypeOpenAI {

output/schema/schema.json

@@ -29,7 +29,7 @@ import { InferenceChunkingSettings } from '@inference/_types/Services'
 /**
  * Create a Mistral inference endpoint.
  *
- * Creates an inference endpoint to perform an inference task with the `mistral` service.
+ * Create an inference endpoint to perform an inference task with the `mistral` service.
  * @rest_spec_name inference.put_mistral
  * @availability stack since=8.15.0 stability=stable visibility=public
  * @availability serverless stability=stable visibility=public
@@ -45,8 +45,7 @@ export interface Request extends RequestBase {
   ]
   path_parts: {
     /**
-     * The task type.
-     * The only valid task type for the model to perform is `text_embedding`.
+     * The type of the inference task that the model will perform.
      */
     task_type: MistralTaskType
     /**