Relocate all Bridgetown Roda logic to new bridgetown_server plugin

[jaredcwhite]

This is an alternate take on the concepts brought forth by @michaelherold in #706

Rather than have RodaApp subclass from a Bridgetown-specific subclass of Roda, you can simply subclass from Roda like any standard Roda application, and then use the bridgetown_stack* plugin to pull in all of Bridgetown's setup.

This provides the added benefits of future improvements where some of the ways in which the stack plugin sets up the app could be further configurable as plugin options.

* Still thinking about the best name to call this. Also there's opportunity to consolidate some of the existing plugin(s) into this new one.

** Thinking of going with bridgetown_init unless there are any objections.

*** Core team consensus was to go with bridgetown_server – thanks @KonnorRogers!

[render]

Your Render PR Server URL is https://bridgetown-api-pr-737.onrender.com.

Follow its progress at https://dashboard.render.com/static/srv-cgkcb068h4931r1vlomg.

[render]

Your Render PR Server URL is https://bridgetown-beta-pr-737.onrender.com.

Follow its progress at https://dashboard.render.com/static/srv-cgkcb0m8h4931r1vlopg.

[jaredcwhite]

@michaelherold I'm curious what your thoughts are on this PR!

[ayushn21]

Can we just call the plugin bridgetown? I think a Roda plugin called bridgetown makes the most sense if we can do that ...

[jaredcwhite]

@ayushn21 I believe I tried that and ran into some annoying namespace issues, but I'll see if I can come up with a workaround. I agree that would probably be ideal.

[brandondrew]

bridgetown_server seems like the clearest possible name 👍

[jaredcwhite]

LGTM!

[michaelherold]

I think that this will make testing easier without using integration tests, but haven't had the creative energy available to test it. Good idea, Jared!

Once I am able, I will post an experience report on the new structure.