Add migration to change environment_roles role column from string to

enum type.
Fix tests and functions affected by the column type change.

templates/applications/fragments/members.html

@@ -126,7 +126,7 @@
                         {{ env.environment_name }}
                       </span>
                       <span class="env-role__role">
-                        : {{ env.role }}
+                        : {{ env.role.value }}
                       </span>
                     </div>
                   {% endfor %}