[MM-62427] Add message attachments validation (#30180)

* Add message attachments validation

* Add props validation

* Validate slack attachment fields

* Update tests and library usage

* Improve interactive dialog error for length checks

* Allow predefined colors for slack attachments

* Fix TestPostAction

* Use const for data source

* Add tests

* Cleanup unused props

* Add happy path tests

* lint fixes

* Add validation for PostActionOptions

server/channels/api4/integration_action_test.go

@@ -39,7 +39,7 @@ func (th *testHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	assert.NotEmpty(th.t, poir.TeamName)
 	assert.NotEmpty(th.t, poir.PostId)
 	assert.NotEmpty(th.t, poir.TriggerId)
-	assert.Equal(th.t, "button", poir.Type)
+	assert.Equal(th.t, model.PostActionTypeButton, poir.Type)
 	assert.Equal(th.t, "test-value", poir.Context["test-key"])
 	_, err = w.Write([]byte("{}"))
 	require.NoError(th.t, err)
@@ -118,7 +118,7 @@ func TestPostActionCookies(t *testing.T) {
 				CreateAt:  model.GetMillis(),
 				UpdateAt:  model.GetMillis(),
 				Props: map[string]any{
-					"attachments": []*model.SlackAttachment{
+					model.PostPropsAttachments: []*model.SlackAttachment{
 						{
 							Title:     "some-title",
 							TitleLink: "https://some-url.com",

server/channels/api4/post_test.go

@@ -1420,7 +1420,7 @@ func TestUpdatePost(t *testing.T) {
 			ChannelId: channel.Id,
 			Message:   "zz" + model.NewId() + " update post 3",
 		}
-		up4.AddProp("attachments", []model.SlackAttachment{
+		up4.AddProp(model.PostPropsAttachments, []model.SlackAttachment{
 			{
 				Text: "Hello World",
 			},
@@ -1772,12 +1772,12 @@ func TestPatchPost(t *testing.T) {
 				Text: "Hello World",
 			},
 		}
-		patch2.Props = &model.StringInterface{"attachments": attachments}
+		patch2.Props = &model.StringInterface{model.PostPropsAttachments: attachments}
 
 		var rpost2 *model.Post
 		rpost2, _, err = client.PatchPost(context.Background(), post.Id, patch2)
 		require.NoError(t, err)
-		assert.NotEmpty(t, rpost2.GetProp("attachments"))
+		assert.NotEmpty(t, rpost2.GetProp(model.PostPropsAttachments))
 		assert.NotEqual(t, rpost.EditAt, rpost2.EditAt)
 	})
 
@@ -4682,7 +4682,7 @@ func TestGetPostStripActionIntegrations(t *testing.T) {
 		ChannelId: th.BasicChannel.Id,
 		Message:   "with slack attachment action",
 	}
-	post.AddProp("attachments", []*model.SlackAttachment{
+	post.AddProp(model.PostPropsAttachments, []*model.SlackAttachment{
 		{
 			Text: "Slack Attachment Text",
 			Fields: []*model.SlackAttachmentField{
@@ -4694,7 +4694,7 @@ func TestGetPostStripActionIntegrations(t *testing.T) {
 			},
 			Actions: []*model.PostAction{
 				{
-					Type: "button",
+					Type: model.PostActionTypeButton,
 					Name: "test-name",
 					Integration: &model.PostActionIntegration{
 						URL: "https://test.test/action",
@@ -4713,7 +4713,7 @@ func TestGetPostStripActionIntegrations(t *testing.T) {
 
 	actualPost, _, err := client.GetPost(context.Background(), rpost.Id, "")
 	require.NoError(t, err)
-	attachments, _ := actualPost.Props["attachments"].([]any)
+	attachments, _ := actualPost.Props[model.PostPropsAttachments].([]any)
 	require.Equal(t, 1, len(attachments))
 	att, _ := attachments[0].(map[string]any)
 	require.NotNil(t, att)