Support GitHub Enterprise avatars via Enterprise REST service and optionally Gravatar

[kabel]

In GitHub Enterprise, the avatarUrl endpoints that the APIs return require authentication in standard configuration. There is currently no way to do token authentication to these endpoints, so a fallback is necessary to render an image.

The interface was previously coded to handle fallback to the Gravatar service (just like GitHub Desktop did), but this behavior was disabled in 13ab0a7 and 6769dd4 because of end-user preference for making this feature configurable.

Recently an enterprise-only REST API was discovered that allows us to proxy the avatar image. This allows us to fetch the binary and encode it as a data URI to inject into the various views that otherwise render the avatar with standard http requests. If this API fails for some reason, Gravatar remains an optional fallback choice.

A new setting githubPullRequests.defaultGravatarsStyle has been added of type enum with values for each of the Gravatar supported fallback styles. Setting this value to none (the default) disables Gravatar integration.

These settings provide a richer user experience for GitHub Enterprise pull requests, allowing users to opt-in/out on avatar rendering via a third-party service with multiple options for the default fallback image style.

For consistency in multiple interface areas where <Avatar> is rendered, the GraphQL queries (and matching typescript interfaces) have been updated to include the necessary email property for integration with Gravatar.

REST provided actors are missing email. If missing email and using GitHub Enterprise and it's needed by Gravatar, make another REST API call to the user endpoint to get email. This allows a fallback avatar to be generated.

This fixes GitHub Enterprise avatars not being rendered in the tree views too.

The utility functions have been adjusted to support doing the fallback image URL generation directly after the raw results have been loaded from the normal REST and GraphQL APIs. This should be a cleaner implementation.

[kabel]

This is a long overdue PR requested by @alexr00

[kabel]

Example Overview render with default settings:

Now with real GitHub Enterprise Avatars (in tree view):

Including avatars for GitHub Enterprise app/integrations:

[kabel]

Looks like I'm referencing outdated information. GitHub Desktop now appears to be using an undocumented GitHub Enterprise REST API endpoint at /api/v3/enterprise/avatars/u/e?email=

[alexr00]

Thank you for the PR! I've pushed a commit with a few small changes (nothing functional, just to make it easier for me to review).

I'm seeing a discrepancy with which avatars are shown in the description page with this change:

I've also left a few comments with some questions/concerns I have.

[kabel]

Thanks for the review/questions.

Based on the availability of the Enterprise REST API (as now used in GitHub Desktop), I added a bit of scope creep to this request. In c0145681df76ef688929ab21181245974db7725e the fallback logic will first check the REST API for the avatar image binary. If the API returns the image binary, it is converted to a data URI to be rendered by the webviews and treeviews. I updated the CSP meta of the webviews to allow img-src data: to make that work. If that's too much for this PR, I can save that commit for a future request.

Other comments that don't require additional feedback should now be addressed.

[alexr00]

I'm sorry @kabel but this PR has become too big for me to continue reviewing now and it mostly seems to be because of fetching the user email when parsing user results from the GitHub REST API. I started reviewing and left some comments, but scope of this change has just gotten to big for me to review at this time.

I will try to plan time to review in the next couple months, but ideally the PR would be much smaller.

Thank you again for this change. If I hear from users that gravatars are important I will definitely reference your changes to see how to enable them.

[alexr00]

I've opened an issue to try to gauge how much desire there is for this feature: #4517

[kabel]

Sounds fair @alexr00. I've got the latest push down to a more manageable size (mostly added lines for the new Enterprise REST integration), but I'll wait for more time to become available. Having a better Enterprise experience continues to be important for me, but I can understand how avatars aren't going to be a huge win feature-wise for folks.