feat: Add OpenAPI documentation for Llama Stack Modular UI BFF

- Add comprehensive OpenAPI 3.0 specification for BFF endpoints
- Include /api/v1/query endpoint for RAG and chat completion
- Add vector database management endpoints
- Include model management endpoints
- Fix CORS configuration for healthcheck endpoint to enable Swagger UI
- Document only public-facing models and remove authentication requirements
- Add common schemas and responses in separate lib/common.yaml file

The OpenAPI documentation can be visualized using Swagger UI or any OpenAPI viewer.
Run the BFF with: make run STATIC_ASSETS_DIR=../frontend/dist MOCK_LS_CLIENT=true ALLOWED_ORIGINS="*"

Author: Matias Schimuneck

frontend/packages/llama-stack-modular-ui/bff/internal/api/app.go

@@ -154,7 +154,7 @@ func (app *App) Routes() http.Handler {
 	healthcheckMux := http.NewServeMux()
 	healthcheckRouter := httprouter.New()
 	healthcheckRouter.GET(HealthCheckPath, app.HealthcheckHandler)
-	healthcheckMux.Handle(HealthCheckPath, app.RecoverPanic(app.EnableTelemetry(healthcheckRouter)))
+	healthcheckMux.Handle(HealthCheckPath, app.RecoverPanic(app.EnableTelemetry(app.EnableCORS(healthcheckRouter))))
 
 	// Combines the healthcheck endpoint with the rest of the routes
 	combinedMux := http.NewServeMux()

frontend/packages/llama-stack-modular-ui/bff/openapi/src/lib/common.yaml

@@ -0,0 +1,73 @@
+components:
+  schemas:
+    Error:
+      type: object
+      required:
+        - code
+        - message
+      properties:
+        code:
+          type: string
+          example: "400"
+        message:
+          type: string
+          example: "Bad request"
+
+    ErrorEnvelope:
+      type: object
+      required:
+        - error
+      properties:
+        error:
+          $ref: "#/components/schemas/Error"
+
+    Envelope:
+      type: object
+      required:
+        - data
+      properties:
+        data:
+          type: object
+          description: The main response data
+        metadata:
+          type: object
+          description: Optional metadata about the response
+
+  responses:
+    BadRequest:
+      description: Bad Request
+      content:
+        application/json:
+          schema:
+            $ref: "#/components/schemas/ErrorEnvelope"
+
+    Unauthorized:
+      description: Unauthorized
+      content:
+        application/json:
+          schema:
+            $ref: "#/components/schemas/ErrorEnvelope"
+
+    NotFound:
+      description: Not Found
+      content:
+        application/json:
+          schema:
+            $ref: "#/components/schemas/ErrorEnvelope"
+
+    InternalServerError:
+      description: Internal Server Error
+      content:
+        application/json:
+          schema:
+            $ref: "#/components/schemas/ErrorEnvelope"
+
+  securitySchemes:
+    Bearer:
+      type: http
+      scheme: bearer
+      bearerFormat: JWT
+      description: Bearer token authentication using OAuth2 JWT tokens
+
+security:
+  - Bearer: []