Have DiscussionXBlock take care of loading JS and CSS files it depends on.

* Add openedx.core.lib.xblock_builtin.get_css_dependencies and get_js_dependencies,
  which respect PIPELINE_ENABLED setting when determining dependencies.
* Move new discussion-related Sass files into discussion subdirectory.
* Use "load_unicode" instead of "render_template" to load JS to add to fragment for DiscussionXBlock.
* Remove unused "course" parameter from context for DiscussionXBlock.student_view.
* Add RTL stylesheet for DiscussionXBlock, and enable the block to load correct stylesheet.
* Load MathJax only once, and include code for configuring MathJax in discussion bundle.
* Make sure username renders correctly in DiscussionXBlock response header.
* Move WYSIWYIG Markdown editor styles to _build-discussion.scss.
* Remove unnecessary import of discussion/utilities/v1-compatibility from _build-discussion.scss.
* Keep courseware-chromeless.html in sync with courseware.html.
* Load CSS for discussions on Teams tab.  This makes it possible to remove CSS for discussions from Sass files for "Course" tab.
* Load js/src/tooltip_manager.js, jquery.autocomplete.js and jquery.autocomplete.css on "Course" tab.

openedx/core/lib/tests/test_xblock_utils.py

@@ -22,7 +22,11 @@ from openedx.core.lib.xblock_utils import (
     replace_jump_to_id_urls,
     replace_course_urls,
     replace_static_urls,
-    sanitize_html_id
+    sanitize_html_id,
+)
+from openedx.core.lib.xblock_builtin import (
+    get_css_dependencies,
+    get_js_dependencies,
 )
 
 
@@ -181,3 +185,41 @@ class TestXblockUtils(SharedModuleStoreTestCase):
         clean_string = sanitize_html_id(dirty_string)
 
         self.assertEqual(clean_string, 'I_have_un_allowed_characters')
+
+    @ddt.data(
+        (True, ["combined.css"]),
+        (False, ["a.css", "b.css", "c.css"]),
+    )
+    @ddt.unpack
+    def test_get_css_dependencies(self, pipeline_enabled, expected_css_dependencies):
+        """
+        Verify that `get_css_dependencies` returns correct list of files.
+        """
+        pipeline_css = {
+            'style-group': {
+                'source_filenames': ["a.css", "b.css", "c.css"],
+                'output_filename': "combined.css"
+            }
+        }
+        with self.settings(PIPELINE_ENABLED=pipeline_enabled, PIPELINE_CSS=pipeline_css):
+            css_dependencies = get_css_dependencies("style-group")
+            self.assertEqual(css_dependencies, expected_css_dependencies)
+
+    @ddt.data(
+        (True, ["combined.js"]),
+        (False, ["a.js", "b.js", "c.js"]),
+    )
+    @ddt.unpack
+    def test_get_js_dependencies(self, pipeline_enabled, expected_js_dependencies):
+        """
+        Verify that `get_js_dependencies` returns correct list of files.
+        """
+        pipeline_js = {
+            'js-group': {
+                'source_filenames': ["a.js", "b.js", "c.js"],
+                'output_filename': "combined.js"
+            }
+        }
+        with self.settings(PIPELINE_ENABLED=pipeline_enabled, PIPELINE_JS=pipeline_js):
+            js_dependencies = get_js_dependencies("js-group")
+            self.assertEqual(js_dependencies, expected_js_dependencies)