feat: add plugin slot for course card action

[jsnwesson]

This PR makes the first step toward removing the Upgrade Button from Learner Dashboard's core functionality, by creating a CourseCardActionSlot whose default component is the Upgrade Button. A follow up PR will remove the default component entirely, as well as remove the source code itself.

To test this locally:

1. Pull down this branch into your local environment
2. In the env.config.js file in your root directory, add the following configuration. To toggle the default component, you can adjust the keepDefault.

import { DIRECT_PLUGIN, PLUGIN_OPERATIONS } from '@openedx/frontend-plugin-framework';

const config = {
  pluginSlots: {
    course_card_action_slot: {
      keepDefault: false,
      plugins: [
        {
          // Insert custom content after course card buttons
          op: PLUGIN_OPERATIONS.Insert,
          widget: {
            id: 'custom_course_card_action',
            priority: 60,
            type: DIRECT_PLUGIN,
            RenderWidget: ({cardId}) => (
              <div>
                <p>📚: {cardId}</p>
              </div>
            ),
          },
        },
      ]
    }
  },
}

export default config;

Current Default Content in CourseCardActionSlot:

Replacing Default Content in CourseCardActionSlot:

Using props passed into PluginSlot

Contributes to: #438 #297

[MaxFrank13]

Just a couple nit picks. Thanks for setting this one up!

[arbrandes]

As per the conversation in today's FWG meeting, this is fine for now.

[jsnwesson]

@sarina here's some screenshots, which I actually liked the custom button example so much that that's what is now going into the repo documentation for this plugin slot!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.25%. Comparing base (a174abb) to head (c9aadd5).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #464   +/-   ##
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  Coverage   97.24%   97.25%           
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  Files         154      155    +1     
  Lines        1378     1383    +5     
  Branches      228      229    +1     
=======================================
+ Hits         1340     1345    +5     
  Misses         36       36           
  Partials        2        2           

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[brian-smith-tcril]

This example looks wonderful now! Super pretty.

Would you mind updating one of the buttons to include something about the cardId? One thing I really liked about the example you had before was that it demonstrated the pluginProps being used.

[jsnwesson]

Good idea, I sure can!

[sarina]

Thank you this is perfect!