[feature] More consistent API error handling (#637)

* update templates

* start reworking api error handling

* update template

* return AP status at web endpoint if negotiated

* start making api error handling much more consistent

* update account endpoints to new error handling

* use new api error handling in admin endpoints

* go fmt ./...

* use api error logic in app

* use generic error handling in auth

* don't export generic error handler

* don't defer clearing session

* user nicer error handling on oidc callback handler

* tidy up the sign in handler

* tidy up the token handler

* use nicer error handling in blocksget

* auth emojis endpoint

* fix up remaining api endpoints

* fix whoopsie during login flow

* regenerate swagger docs

* change http error logging to debug

web/template/404.tmpl

@@ -2,7 +2,17 @@
 <main>
 	<section>
 		<h1>404: Page Not Found</h1>
-		If you believe this was an error, you can <a href="{{.instance.ContactAccount.URL}}">contact an admin</a>
+		<p>
+			GoToSocial only serves Public statuses via the web.
+			If you reached this page by clicking on a status link,
+			it's possible that the status is not Public, has been
+			deleted by the author, you don't have permission to see
+			it, or it just doesn't exist at all.
+		</p>
+		<p>
+			If you believe this 404 was an error, you can contact
+			the instance admin.
+		</p>
 	</section>
 </main>
 

web/template/error.tmpl

@@ -3,6 +3,5 @@
         <section class="error">
           <span>❌</span> <pre>{{.error}}</pre>
         </section>
-        
     </main>
 {{ template "footer.tmpl" .}}

web/template/footer.tmpl

@@ -5,10 +5,14 @@
 			<a href="https://github.com/superseriousbusiness/gotosocial">Source Code</a>
 		</div>
 		<div id="contact">
+			{{ if .instance.ContactAccount }}
 			Contact: <a href="{{.instance.ContactAccount.URL}}" class="nounderline">{{.instance.ContactAccount.Username}}</a><br>
+			{{ end }}
 		</div>
 		<div id="email">
+			{{ if .instance.Email }}
 			Email: <a href="mailto:{{.instance.Email}}" class="nounderline">{{.instance.Email}}</a><br>
+			{{ end }}
 		</div>
 	</footer>
 </body>