build(staticman): use wd15-staticman.herokuapp.com

[wd15]

Address #899

Use wd15-staticman.herokuapp.com instead of https://dev.staticman.net
for new PFHub Staticman instance hosted on Heroku.

Running up against "Application Error' when using https://dev.staticman.net, which is the public instance of Staticman. Decided to roll out a PFHub dedicated Staticman hosted on the free tier of Heroku. Hopefully, this will be more stable going forward. Also, will give us more flexibility to adjust the way Staticman works and more easily interact with out Python backend app.

Currently using this version of staticman.

These changes can be viewed live.

Remember to tear down the live site when merging
or closing this pull request.

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This change is 

[tkphd]

"More stable" in that we expect Heroku to have better uptime than Staticman?

[tkphd]

@wd15, please comment on the impact of this change on maintainability of PFHub.

[wd15]

Few reasons for this change (nothing to do with uptime or Heroku as the public instance is also hosted from Heroku):

• the public instance keeps changing and breaking due to changes that aren't documented or due to GitHub API limits
• the main contributor is no longer responding much on GitHub (31 oepn pull requests) so changes aren't documented other than in issue comments which are hard to track
• there are other public instances, but it's very easy to deploy and safer to have our own instance
• it's very easy to change between different instances if necessary so it isn't much of issue switching between instances
• the endpoint will just stay the same unless I actually want to change make a change
• we can start adding features like GitHub authentication into our own version (which we can choose to push back if the main developed becomes active again)

Some relevant comments:

• 503 error using v3 endpoint eduardoboucas/staticman#307 (comment)
• "Application error" when trying to connect a new repository eduardoboucas/staticman#296
• Make a staticman app instead of staticmanapp to avoid reaching quotas eduardoboucas/staticman#243 (comment)
• "Application error" when trying to connect a new repository eduardoboucas/staticman#296 (comment)
• Setting up the v3 endpoint (503 error) eduardoboucas/staticman#294 (comment)
• Cors Proxy Issue eduardoboucas/staticman#278 (comment)

[wd15]

@wd15, please comment on the impact of this change on maintainability of PFHub.

It'll make it easier to maintain if anything as we won't have to deal with Staticman end points changing and having no control over the app.

[tkphd]

LGTM