Add prefix_string config option for ML models (#2451)

* Add prefix_string config option for ML models (#2363)

The prefix_strings option was added to support the E5 model in
elastic/elasticsearch#102089

* Add prefix_strings option to PUT model request (#2449)

Follow up to #2363 where prefix_strings option was added to TrainedModelConfig

Author: davidkyle

output/openapi/elasticsearch-serverless-openapi.json

@@ -196,6 +196,7 @@ export class TrainedModelConfig {
   metadata?: TrainedModelConfigMetadata
   model_size_bytes?: ByteSize
   location?: TrainedModelLocation
+  prefix_strings?: TrainedModelPrefixStrings
 }
 
 export class TrainedModelConfigInput {
@@ -423,3 +424,14 @@ export class TrainedModelLocation {
 export class TrainedModelLocationIndex {
   name: IndexName
 }
+
+export class TrainedModelPrefixStrings {
+  /**
+   * String prepended to input at ingest
+   */
+  ingest?: string
+  /**
+   * String prepended to input at search
+   */
+  search?: string
+}

output/schema/schema.json

@@ -22,6 +22,7 @@ import { RequestBase } from '@_types/Base'
 import { Id } from '@_types/common'
 import { long } from '@_types/Numeric'
 import { Definition, Input } from './types'
+import { TrainedModelPrefixStrings } from '../_types/TrainedModel'
 import { TrainedModelType } from '../_types/TrainedModel'
 import { InferenceConfigCreateContainer } from '@ml/_types/inference'
 
@@ -102,5 +103,11 @@ export interface Request extends RequestBase {
      * An array of tags to organize the model.
      */
     tags?: string[]
+    /**
+     * Optional prefix strings applied at inference
+     * @availability stack since=8.12.0
+     * @availability serverless
+     */
+    prefix_strings?: TrainedModelPrefixStrings
   }
 }