Plugins: Refactor GetPluginDashboards/LoadPluginDashboard (#46316)

Refactors GetPluginDashboards/LoadPluginDashboard by moving database 
interaction from plugin management to the plugindashboards service.

Fixes #44553

Co-authored-by: Will Browne <wbrowne@users.noreply.github.com>

pkg/web/webtest/webtest.go

@@ -49,6 +49,16 @@ func NewServer(t testing.TB, routeRegister routing.RouteRegister) *Server {
 	}
 }
 
+// NewGetRequest creates a new GET request setup for test.
+func (s *Server) NewGetRequest(target string) *http.Request {
+	return s.NewRequest(http.MethodGet, target, nil)
+}
+
+// NewPostRequest creates a new POST request setup for test.
+func (s *Server) NewPostRequest(target string, body io.Reader) *http.Request {
+	return s.NewRequest(http.MethodPost, target, body)
+}
+
 // NewRequest creates a new request setup for test.
 func (s *Server) NewRequest(method string, target string, body io.Reader) *http.Request {
 	s.t.Helper()
@@ -65,11 +75,19 @@ func (s *Server) NewRequest(method string, target string, body io.Reader) *http.
 	return req
 }
 
-// Send sends an HTTP request to the test server and returns an HTTP response
+// Send sends a HTTP request to the test server and returns an HTTP response.
 func (s *Server) Send(req *http.Request) (*http.Response, error) {
 	return http.DefaultClient.Do(req)
 }
 
+// SendJSON sets the Content-Type header to application/json and sends
+// a HTTP request to the test server and returns an HTTP response.
+// Suitable for POST/PUT/PATCH requests that sends request body as JSON.
+func (s *Server) SendJSON(req *http.Request) (*http.Response, error) {
+	req.Header.Add("Content-Type", "application/json")
+	return s.Send(req)
+}
+
 func generateRequestIdentifier() string {
 	return uuid.NewString()
 }
@@ -91,7 +109,7 @@ func RequestWithWebContext(req *http.Request, c *models.ReqContext) *http.Reques
 
 func RequestWithSignedInUser(req *http.Request, user *models.SignedInUser) *http.Request {
 	return RequestWithWebContext(req, &models.ReqContext{
-		SignedInUser: &models.SignedInUser{},
+		SignedInUser: user,
 		IsSignedIn:   true,
 	})
 }