Upgrade to Phoenix 1.6.0-rc.0

[kinson]

Overview

This pr updates does 2 things:

• updates the version of Phoenix from 1.5.9 to 1.6.0-rc.0 and makes the corresponding file changes to support it
• removes ecto-related dependencies and boilerplate since we are not using it for this project

This pr is ~very much a WIP - the remaining items~ ready to go!:

• [x] make sure this branch can deploy to Heroku smoothly
• [x] update live templates to use the new heex hotness 🔥
• [x] remove remaining webpack/js related configuratoin
• [x] fix dialyzer error
• [x] fix console error message casued by Alpine.start()
• [x] fix topbar dependency integration

References

Of course I could not have done this without Chris & Jose's guidance ❤️ in these two guides:

• https://gist.github.com/chrismccord/2ab350f154235ad4a4d0f4de6decba7b
• https://github.com/josevalim/phx_esbuild_demo/pull/3

[doomspork]

@kinson are we ready to convert this into a PR?

[kinson]

@kinson are we ready to convert this into a PR?

This pr is ready 🎉 ! I am not sure if this is possible, but do you mind redeploying this branch on Heroku so we can take a look before merging and do some manual testing there?

Two other notes about this pr:

• I am not sure if we want to merge a pre released version of Phoenix, though I haven't heard of any significant regressions or bugs
• In a separate pr I will convert the remaining templates to heex - I can do it here instead but it would balloon the size of this pr siginificantly and eex/leex templates are still supported in 1.6

[doomspork]

@kinson sounds good! I will let you know when I deploy this (may be a little bit).

[kinson]

Since Phoenix 1.6.0 has been officially released, I will upgrade to it before this pr gets merged 🎊