Improve communication of API status issues to external/internal users

[dorothyyeager]

What we are after

Need to come up with a way to alert users to API status issues. This might be best accomplished by improving the message for our 500 errors, so that users are given more information than "server error."

Related issues

#966 - Original implementation issue

To do

• Consider creating API status page or linking Pingdom's page for it at http://stats.pingdom.com/x0blqgj29ogg
• Change pingdom URL to status.fec.gov
  (See https://help.pingdom.com/hc/en-us/articles/205386171-Public-Status-Page).
• Draft message for 500 server errors (when the page is down due to API issues and can't be accessed by user). Message could link to above status page.
• [ ] High level review of message
• Create implementation ticket

[dorothyyeager]

I've made a first stab at drafting a new message and sent to @AmyKort @patphongs @PaulClark2 for their thoughts. In doing this, I looked at our revised 404 error message in #2675 plus worked in our discussion about the API status pingdom page. We'll need someone with access to change the URL in pingdom for that page.

Once we finalize the draft, we can send it around for a high level review as needed.

[dorothyyeager]

For reference, here's the current message.

[dorothyyeager]

@PaulClark2 and @AmyKort have signed off on the draft message. We'll see if we need to run it any higher. We've also changed the pingdom URL to http://status.fec.gov/x0blqgj29ogg.

[dorothyyeager]

The message has been drafted and approved, so we're ready to move on to implementation ticket.
That work will happen in #3113 .