MM-27909: Add manage_shared_channels permission (#15601)

* MM-27909: Add manage_shared_channels permission

We add a new permission to manage shared channels.

It's a channel scoped permission and only the system admin
has that by default.

https://mattermost.atlassian.net/browse/MM-27909

* change to system scoped

* Trigger CI

* Trigger CI

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

model/migration.go

@@ -21,4 +21,5 @@ const (
 	MIGRATION_KEY_ADD_SYSTEM_CONSOLE_PERMISSIONS              = "add_system_console_permissions"
 	MIGRATION_KEY_SIDEBAR_CATEGORIES_PHASE_2                  = "migration_sidebar_categories_phase_2"
 	MIGRATION_KEY_ADD_CONVERT_CHANNEL_PERMISSIONS             = "add_convert_channel_permissions"
+	MIGRATION_KEY_ADD_MANAGE_SHARED_CHANNEL_PERMISSIONS       = "manage_shared_channel_permissions"
 )

model/permission.go

@@ -99,6 +99,7 @@ var PERMISSION_USE_CHANNEL_MENTIONS *Permission
 var PERMISSION_USE_GROUP_MENTIONS *Permission
 var PERMISSION_READ_OTHER_USERS_TEAMS *Permission
 var PERMISSION_EDIT_BRAND *Permission
+var PERMISSION_MANAGE_SHARED_CHANNELS *Permission
 
 var PERMISSION_SYSCONSOLE_READ_ABOUT *Permission
 var PERMISSION_SYSCONSOLE_WRITE_ABOUT *Permission
@@ -516,6 +517,12 @@ func initializePermissions() {
 		"authentication.permissions.delete_others_posts.description",
 		PermissionScopeChannel,
 	}
+	PERMISSION_MANAGE_SHARED_CHANNELS = &Permission{
+		"manage_shared_channels",
+		"authentication.permissions.manage_shared_channels.name",
+		"authentication.permissions.manage_shared_channels.description",
+		PermissionScopeSystem,
+	}
 	PERMISSION_REMOVE_USER_FROM_TEAM = &Permission{
 		"remove_user_from_team",
 		"authentication.permissions.remove_user_from_team.name",
@@ -912,6 +919,7 @@ func initializePermissions() {
 		PERMISSION_PROMOTE_GUEST,
 		PERMISSION_DEMOTE_TO_GUEST,
 		PERMISSION_EDIT_BRAND,
+		PERMISSION_MANAGE_SHARED_CHANNELS,
 	}
 
 	TeamScopedPermissions := []*Permission{