Adds EIS inference PUT API (elastic#125082)

Author: szabosteve

rest-api-spec/src/main/resources/rest-api-spec/api/inference.put_eis.json

@@ -0,0 +1,35 @@
+{
+    "inference.put_eis": {
+      "documentation": {
+        "url": "https://www.elastic.co/guide/en/elasticsearch/reference/current/infer-service-elastic.html",
+        "description": "Configure an inference endpoint that uses the Elastic Inference Service (EIS)"
+      },
+      "stability": "stable",
+      "visibility": "public",
+      "headers": {
+        "accept": ["application/json"],
+        "content_type": ["application/json"]
+      },
+      "url": {
+        "paths": [
+          {
+            "path": "/_inference/{task_type}/{eis_inference_id}",
+            "methods": ["PUT"],
+            "parts": {
+              "task_type": {
+                "type": "string",
+                "description": "The task type"
+              },
+              "eis_inference_id": {
+                "type": "string",
+                "description": "The inference ID"
+              }
+            }
+          }
+        ]
+      },
+      "body": {
+        "description": "The inference endpoint's task and service settings"
+      }
+    }
+  }