MDL-84387 mod_assign: Improve submission confirmation with file list

This add the ability for assingment submission plugins to summarise
what was submitted, and then that summary is included in the
message to students confirming to them that their submission
was received.

Then, this new API is implemented in the file and online text plugins.

Co-authored-by: Tim Hunt <[email protected]>

mod/assign/renderable.php

@@ -701,7 +701,7 @@ class assign_course_index_summary implements renderable {
 class assign_files implements renderable {
     /** @var context $context */
     public $context;
-    /** @var string $context */
+    /** @var array $dir as returned by {@see file_storage::get_area_tree()}. */
     public $dir;
     /** @var MoodleQuickForm $portfolioform */
     public $portfolioform;
@@ -799,4 +799,6 @@ class assign_files implements renderable {
             true,
         );
     }
+
+
 }