FIX: Render user profile trust level name for TL0 (#22740)

* Why was this change necessary?
The current logic in the user.hbs template file does not render the
trust level element for the user's info panel when the user is TL0,
because 0 is treated as falsey in the `if` conditional block.

Ref: https://meta.discourse.org/t/tl0-not-displayed-on-users-profile-pages/271779/10

* How does it address the problem?

This PR adds a predicate helper method local to the user controller that
includes an additional check which returns true if the trust_level of
the user is 0 on top of the existing logic. This allows TL0 users to
have their trust level rendered correctly in their profile's info panel.

app/assets/javascripts/discourse/app/controllers/user.js

@@ -68,6 +68,8 @@ export default Controller.extend(CanCheckEmails, {
     };
   }),
 
+  isTrustLevelZero: equal("model.trust_level", 0),
+  hasTrustLevel: or("isTrustLevelZero", "model.trust_level"),
   showStaffCounters: or(
     "hasGivenFlags",
     "hasFlaggedPosts",

app/assets/javascripts/discourse/app/templates/user.hbs

@@ -384,7 +384,7 @@
                       @model={{this.model.invited_by}}
                     >{{this.model.invited_by.username}}</LinkTo></dd></div>
               {{/if}}
-              {{#if this.model.trust_level}}
+              {{#if this.hasTrustLevel}}
                 <div><dt class="trust-level">{{i18n "user.trust_level"}}</dt><dd
                     class="trust-level"
                   >{{this.model.trustLevel.name}}</dd></div>

spec/system/page_objects/pages/user.rb

@@ -29,6 +29,12 @@ module PageObjects
         staff_counters.find("a[href='/u/#{user.username}/messages/warnings']").click
         self
       end
+
+      def expand_info_panel
+        button = page.find("button[aria-controls='collapsed-info-panel']")
+        button.click if button["aria-expanded"] == "false"
+        self
+      end
     end
   end
 end

spec/system/user_page/user_profile_info_panel_spec.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+RSpec.describe "User Profile Info Panel", system: true do
+  let(:user_page) { PageObjects::Pages::User.new }
+
+  describe "trust level" do
+    TrustLevel.levels.values.each do |trust_level|
+      context "when user has trust level #{trust_level}" do
+        fab!(:user) { Fabricate(:user, trust_level: trust_level) }
+        before { sign_in(user) }
+
+        it "displays the correct trust level element" do
+          user_page.visit(user).expand_info_panel
+          expect(user_page).to have_css("dd.trust-level", text: TrustLevel.name(trust_level))
+        end
+      end
+    end
+  end
+end