Update shortcut URL page with extra warning text

Author: cslzchen

src/main/resources/messages.properties

@@ -611,6 +611,7 @@ screen.institutionlogin.message.auto=Your institution has partnered with OSF. Pl
 screen.institutionlogin.heading.select=Your institution
 screen.institutionlogin.heading.auto=Your institution
 screen.institutionlogin.link.select=Not your institution?
+screen.institutionlogin.link.hidden=placeholder: here goes some warning message
 screen.institutionlogin.link.unsupported=I can't find my institution
 screen.institutionlogin.button.submit=Sign in
 screen.institutionlogin.osf=Sign in with email

src/main/resources/templates/casInstitutionLoginView.html

@@ -31,6 +31,10 @@ <h1 th:utext="#{screen.institutionlogin.heading}"></h1>
                         </select>
                     </section>
 
+                    <section class="text-with-mdi text-danger">
+                            <p th:if="${osfCasLoginContext.institutionId}" th:utext="#{screen.institutionlogin.link.hidden}"></p>
+                    </section>
+
                     <section class="text-with-mdi">
                         <span th:if="${osfCasLoginContext.institutionId}">
                             <a th:href="@{/login(campaign=institution, institutionId=${institutionId ?: ''}, service=${service?.originalUrl ?: ''})}" th:utext="#{screen.institutionlogin.link.select}"></a>