API: Extract OpenAPI specification from source code using go-swagger (#40528) (#45061)

* API: Using go-swagger for extracting OpenAPI specification from source code

* Merge Grafana Alerting spec

* Include enterprise endpoints (if enabled)

* Serve SwaggerUI under feature flag

* Fix building dev docker images

* Configure swaggerUI

* Add missing json tags

Co-authored-by: Ying WANG <ying.wang@grafana.com>
Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>
(cherry picked from commit 35fe58de37)

pkg/api/docs/definitions/responses.go

@@ -0,0 +1,83 @@
+package definitions
+
+// A GenericError is the default error message that is generated.
+// For certain status codes there are more appropriate error structures.
+//
+// swagger:response genericError
+type GenericError struct {
+	// The response message
+	// in: body
+	Body ErrorResponseBody `json:"body"`
+}
+
+type ErrorResponseBody struct {
+	// a human readable version of the error
+	// required: true
+	Message string `json:"message"`
+
+	// Error An optional detailed description of the actual error. Only included if running in developer mode.
+	Error string `json:"error"`
+
+	// Status An optional status to denote the cause of the error.
+	//
+	// For example, a 412 Precondition Failed error may include additional information of why that error happened.
+	Status string `json:"status"`
+}
+
+// swagger:model
+type SuccessResponseBody struct {
+	Message string `json:"message,omitempty"`
+}
+
+// An OKResponse is returned if the request was successful.
+//
+// swagger:response okResponse
+type OKResponse struct {
+	// in: body
+	Body SuccessResponseBody `json:"body"`
+}
+
+// ForbiddenError is returned if the user/token has insufficient permissions to access the requested resource.
+//
+// swagger:response forbiddenError
+type ForbiddenError GenericError
+
+// NotFoundError is returned when the requested resource was not found.
+//
+// swagger:response notFoundError
+type NotFoundError GenericError
+
+// BadRequestError is returned when the request is invalid and it cannot be processed.
+//
+// swagger:response badRequestError
+type BadRequestError GenericError
+
+// ConflictError
+//
+// swagger:response conflictError
+type ConflictError GenericError
+
+// PreconditionFailedError
+//
+// swagger:response preconditionFailedError
+type PreconditionFailedError GenericError
+
+// UnprocessableEntityError
+//
+// swagger:response unprocessableEntityError
+type UnprocessableEntityError GenericError
+
+// InternalServerError is a general error indicating something went wrong internally.
+//
+// swagger:response internalServerError
+type InternalServerError GenericError
+
+// UnauthorizedError is returned when the request is not authenticated.
+//
+// swagger:response unauthorisedError
+type UnauthorizedError GenericError
+
+// AcceptedResponse
+//
+// swagger:response acceptedResponse
+type AcceptedResponse GenericError