Implement create and get incoming webhook endpoints for APIv4 (#5407)

* Implement POST /hooks/incoming endpoint for APIv4

* Implement GET /hooks/incoming endpoint for APIv4

* Updates per feedback

api4/apitestlib.go

@@ -422,6 +422,21 @@ func CheckBadRequestStatus(t *testing.T, resp *model.Response) {
 	}
 }
 
+func CheckNotImplementedStatus(t *testing.T, resp *model.Response) {
+	if resp.Error == nil {
+		debug.PrintStack()
+		t.Fatal("should have errored with status:" + strconv.Itoa(http.StatusNotImplemented))
+		return
+	}
+
+	if resp.StatusCode != http.StatusNotImplemented {
+		debug.PrintStack()
+		t.Log("actual: " + strconv.Itoa(resp.StatusCode))
+		t.Log("expected: " + strconv.Itoa(http.StatusNotImplemented))
+		t.Fatal("wrong status code")
+	}
+}
+
 func CheckErrorMessage(t *testing.T, resp *model.Response, errorId string) {
 	if resp.Error == nil {
 		debug.PrintStack()