API SSO, Beautification of Tables, and more. (#562)

# One Thousandth Commit 🎉 🎈 🎆 🍾

* Allow requiring API ownership validation by SSO.
Closes #163

* Add Discourse group name length restrictions.

* Redirect after api addition/deletion of main character

* Correct admin searching for removed discourse_username field in AuthServicesInfo

* Correct admin function to sync user Discourse groups

* Beautify tables by removing borders and hiding when empty.

*Add buttons on dead-end pages to return to originating view.

authentication/admin.py

@@ -99,7 +99,7 @@ class AuthServicesInfoManager(admin.ModelAdmin):
     def sync_discourse(self, request, queryset):
         count = 0
         for a in queryset:
-            if a.discourse_username != "":
+            if a.discourse_enabled:
                 update_discourse_groups.delay(a.user.pk)
                 count += 1
         self.message_user(request, "%s discourse accounts queued for group sync." % count)
@@ -137,7 +137,6 @@ class AuthServicesInfoManager(admin.ModelAdmin):
         'mumble_username',
         'teamspeak3_uid',
         'discord_uid',
-        'discourse_username',
         'ips4_username',
         'smf_username',
         'market_username',