right sidebar: Clean up rendered description logic.

Previously, we were masking the realm_description raw Markdown with
rendered Markdown, which was a type error.

When we switch to calling /register explicitly in a few commits, this
results in a bug, since the raw Markdown ends up taking priority.

Fix this by just using a different name for this different concept.

static/js/ui_init.js

@@ -157,7 +157,7 @@ function initialize_left_sidebar() {
 function initialize_right_sidebar() {
     const rendered_sidebar = render_right_sidebar({
         can_invite_others_to_realm: settings_data.user_can_invite_others_to_realm(),
-        realm_description: page_params.realm_description,
+        realm_rendered_description: page_params.realm_rendered_description,
     });
 
     $("#right-sidebar-container").html(rendered_sidebar);

static/templates/right_sidebar.hbs

@@ -32,7 +32,7 @@
             </a>
             <div class="only-visible-for-spectators">
                 <div class="realm-description">
-                    <div class="rendered_markdown">{{rendered_markdown realm_description }}</div>
+                    <div class="rendered_markdown">{{rendered_markdown realm_rendered_description }}</div>
                     <hr />
                     <a href="/register"  class="signup_button color_animated_button">
                         <i class="fa fa-pencil-square-o"></i>

zerver/lib/home.py

@@ -243,6 +243,6 @@ def build_page_params_for_home_page_load(
     if user_profile is None:
         # Get rendered version of realm description which is displayed in right
         # sidebar for spectator.
-        page_params["realm_description"] = get_realm_rendered_description(realm)
+        page_params["realm_rendered_description"] = get_realm_rendered_description(realm)
 
     return register_ret["queue_id"], page_params

zerver/tests/test_home.py

@@ -336,8 +336,10 @@ class HomeTest(ZulipTestCase):
             "narrow",
             "narrow_stream",
         ]
-        expected_keys = [i for i in self.expected_page_params_keys if i not in removed_keys]
-        self.assertEqual(actual_keys, expected_keys)
+        expected_keys = set(self.expected_page_params_keys + ["realm_rendered_description"]) - set(
+            removed_keys
+        )
+        self.assertEqual(set(actual_keys), set(expected_keys))
 
         # Test information passed to client about users.
         page_params = self._get_page_params(result)