[MM-44488] Cloud limits: enforcing messages (#20362)

* Add new Job to keep updating the last_accessible_post time

* Filter out posts for funcs returning PostList model

* Separate methods to get and compute cache

* filter pinned posts

* For posts with sorted CreateAt order, support a faster form of filtering.

* Add inaccessible header for getPost and getPostsByIDs APIs

* replace manual binary search with the std. library

* in-place filter posts

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>
Co-authored-by: Nathaniel Allred <neallred@protonmail.com>

api4/post.go

@@ -381,6 +381,7 @@ func getFlaggedPostsForUser(c *Context, w http.ResponseWriter, r *http.Request)
 	}
 }
 
+// getPost also sets a header to indicate, if post is inaccessible due to the cloud plan's limit.
 func getPost(c *Context, w http.ResponseWriter, r *http.Request) {
 	c.RequirePostId()
 	if c.Err != nil {
@@ -396,6 +397,12 @@ func getPost(c *Context, w http.ResponseWriter, r *http.Request) {
 	post, err := c.App.GetPostIfAuthorized(c.Params.PostId, c.AppContext.Session(), includeDeleted)
 	if err != nil {
 		c.Err = err
+
+		// Post is inaccessible due to cloud plan's limit.
+		if err.Id == "app.post.cloud.get.app_error" {
+			w.Header().Set(model.HeaderHasInaccessiblePosts, "true")
+		}
+
 		return
 	}
 
@@ -416,6 +423,7 @@ func getPost(c *Context, w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+// getPostsByIds also sets a header to indicate, if posts were truncated as per the cloud plan's limit.
 func getPostsByIds(c *Context, w http.ResponseWriter, r *http.Request) {
 	postIDs := model.ArrayFromJSON(r.Body)
 
@@ -429,7 +437,7 @@ func getPostsByIds(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	postsList, err := c.App.GetPostsByIds(postIDs)
+	postsList, hasInaccessiblePosts, err := c.App.GetPostsByIds(postIDs)
 	if err != nil {
 		c.Err = err
 		return
@@ -462,6 +470,8 @@ func getPostsByIds(c *Context, w http.ResponseWriter, r *http.Request) {
 		posts = append(posts, post)
 	}
 
+	w.Header().Set(model.HeaderHasInaccessiblePosts, strconv.FormatBool(hasInaccessiblePosts))
+
 	if err := json.NewEncoder(w).Encode(posts); err != nil {
 		mlog.Warn("Error while writing response", mlog.Err(err))
 	}