[MM-44765] Add API method for getting post's information from permalink (#21518)

* add api for getting post's information

* add information about current user state

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

model/client4.go

@@ -8540,6 +8540,20 @@ func (c *Client4) GetNewTeamMembersSince(teamID string, timeRange string, page i
 	return newTeamMembersList, BuildResponse(r), nil
 }
 
+func (c *Client4) GetPostInfo(postId string) (*PostInfo, *Response, error) {
+	r, err := c.DoAPIGet(c.postRoute(postId)+"/info", "")
+	if err != nil {
+		return nil, BuildResponse(r), err
+	}
+	defer closeBody(r)
+
+	var info *PostInfo
+	if err = json.NewDecoder(r.Body).Decode(&info); err != nil {
+		return nil, nil, NewAppError("GetPostInfo", "api.unmarshal_error", nil, "", http.StatusInternalServerError).Wrap(err)
+	}
+	return info, BuildResponse(r), nil
+}
+
 func (c *Client4) AcknowledgePost(postId, userId string) (*PostAcknowledgement, *Response, error) {
 	r, err := c.DoAPIPost(c.userRoute(userId)+c.postRoute(postId)+"/ack", "")
 	if err != nil {