MM-22845: Added support for permalink previews. (#17796)

* MM-22845: Added support for permalink previews.

* MM-22845: Adds license to new file.

* MM-22845: Adds endpoint to retrieve multiple posts by id.

* MM-22845: Fix for deleted post.

* MM-22845: Adds config setting for permalink previews.

* MM-22845: Adds API test for new endpoint.

* MM-22845: Fix typo.

* MM-22845: Tests that post create or updated via App get the previewed_post prop.

* MM-22845: Tests for matching permalinks.

* MM-22845: Adds PreparePostForClient test for permalink previews.

* MM-22845: Embeds entire post in permalink metadata.

* MM-22845: Filter WS message payload of created and edited post based on permissions.

* MM-22845: Runs app layer generator.

* MM-22845: Lint check fix.

* MM-22845: Adds feature flag.

* MM-22845: Clones WS message.

* MM-22845: Removes knowledge of permalink from LinkMetadata table. Removes knowledge of user id from post embedding methods in favour of a 'sanitize' method/step.

* MM-22845: Handle nil post metadata.

* MM-22845: Switch to cloning post.

* MM-22845: Removes unused code.

* MM-22845: Refactor.

* MM-22845: Reverts whitespace change.

* MM-22845: Removes unnecessary code.

* MM-22845: Removes unnecessary function.

* MM-22845: Warn but don't error if permalinked referenced post or channel is not found.

* MM-22845: Fix for clone method.

* MM-22845: Fix for clone method.

* MM-22845: Updates translations.

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

model/post.go

@@ -67,6 +67,8 @@ const (
 
 	PostPropsMentionHighlightDisabled = "mentionHighlightDisabled"
 	PostPropsGroupHighlightDisabled   = "disable_group_highlight"
+
+	PostPropsPreviewedPost = "previewed_post"
 )
 
 type Post struct {
@@ -749,3 +751,14 @@ func (o *Post) ToNilIfInvalid() *Post {
 	}
 	return o
 }
+
+func (o *Post) GetPreviewPost() *PreviewPost {
+	for _, embed := range o.Metadata.Embeds {
+		if embed.Type == PostEmbedPermalink {
+			if previewPost, ok := embed.Data.(*PreviewPost); ok {
+				return previewPost
+			}
+		}
+	}
+	return nil
+}