feat: make api only return json (#42320)

* fix(api): return json for delete + reset-progress

* refactor(api): make .json calls explicit

These .send() calls had objects as arguments. Using .json() makes it
explicit without changing behaviour.

* fix: return json or redirectWithFlash

We should never be getting requests for plain text, but if we do they
should be redirected back to the client.

* fix: prioritize JSON responses

If accepted, respond with JSON.  If not, it's probably a bad request.

api-server/src/server/boot/randomAPIs.js

@@ -193,7 +193,7 @@ module.exports = function (app) {
               pulls === parseInt(pulls, 10) && issues
                 ? Object.keys(JSON.parse(issues)).length - pulls
                 : "Can't connect to GitHub";
-            return res.send({
+            return res.json({
               issues: issues,
               pulls: pulls
             });