Fix broken Firefox extension

[cmsetzer]

Before:

• The Perma.cc extension for Firefox was broken. It would fail on every URL with an error like Firefox can’t find the file at moz-extension://5f641aec-6742-443d-b1c3-feeefc2e0419/https://perma.cc/service/bookmarklet-create/?v=1&url=https://example.com/.
• The error happened because we pass the (absolute) target URL into getURL, which is only meant for relative paths (see [1], [2]). Seems like it only worked by accident before, or maybe they changed the API at some point.

After:

• We no longer use getURL, so the extension now connects to Perma.cc as expected.

How to test

1. In Firefox, go to about:debugging
2. Click "This Firefox" at left
3. Click the "Load Temporary Add-on…" button and select the extras/perma-firefox/src/manifest.json file from this branch
4. Now the local extension should be loaded; navigate to a website and click the Perma.cc extension button to test it out

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.67%. Comparing base (ffa57fa) to head (02b572c).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #3681   +/-   ##
========================================
  Coverage    69.67%   69.67%           
========================================
  Files           54       54           
  Lines         7661     7661           
========================================
  Hits          5338     5338           
  Misses        2323     2323           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[teovin]

Looks good! I followed your instructions and was able to capture a couple of links as expected.

This was my first time playing with this extension, so I would like to confirm the flow quickly: When the extension is clicked, the user is asked to log in. After logging in, they are taken to manage/create, where they are expected to use the create perma link button with the URL prepopulated from the previous step.

[cmsetzer]

Yes, that is the expected behavior. The extension is new to me too, but it's basically a quick way to populate Perma's URL field from the current site. It was created in 2016 and hasn't been touched since, so it's pretty simple.

Thanks for the review! I will look at getting this release published on addons.mozilla.org.