[PR] Add auth

[LuchoTurtle]

closes #1

This PR adds authentication using https://github.com/dwyl/auth_plug.
Instead of usernames being randomly generated and assigned, when a user logs in, his username is shown.

[LuchoTurtle]

After logging in, I can't seem to get access to the socket assigns pertaining to the logged-in user.
No changes to the assigns seem to occur after logging in, contrary to the https://github.com/dwyl/auth_plug docs.

Will further look into this tomorrow, during/after standup.

[Arhell]

cc @nelsonic

[LuchoTurtle]

Gonna have a look at this https://github.com/dwyl/mvp/blob/main/BUILDIT.md#62-create-auth-controller
this should fix whatever problems I'm having.

[LuchoTurtle]

@nelsonic the auth tests are failing because there's no AUTH_API_KEY.
Is there an org one I should use?

The PR is ready and the auth works properly now.

[nelsonic]

We don't have any org-wide AUTH_API_KEY that would be a security anti-pattern.
[don't worry if you didn't know... but it would be like using the same internet password on all websites ...]
We create a new "App" for each instance of auth_plug with a descriptive name
and then have an AUTH_API_KEY that can be easily reset/revoked for that App.
See: #1 (comment)

[codecov]

Codecov Report

Merging #12 (affabd9) into main (fa70062) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main       #12   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         3    +1     
  Lines           22        35   +13     
=========================================
+ Hits            22        35   +13     

Impacted Files	Coverage Δ
...ib/live_cursors_web/controllers/auth_controller.ex	100.00% <100.00%> (ø)
lib/live_cursors_web/live/cursors.ex	100.00% <100.00%> (ø)
lib/live_cursors_web/router.ex	100.00% <100.00%> (ø)

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[nelsonic]

Pending review/merge of: dwyl/auth_plug#88

[LuchoTurtle]

Made the changes to use AuthPlug.assign_jwt_to_socket/3, as discussed. Also formatted the files, in case CI complains about it.

Should be good to go.

[nelsonic]

@LuchoTurtle looks great! Thanks. 👌