Occasionally Yii updates their template for Active Record model files.
It seems more helpful to see the effects of those changes in that same
PR (where Yii was updated), rather than seeing them in a later,
unrelated PR.

Updating the base models only takes around 10 seconds, so it seems like
a minimal time cost (percentage-wise) that we're adding to each composer
update call.

Update base models, and do so with each "make composerupdate"

PHP's `explode()` returns an array with an empty string if the given
string is empty, but we do not want to add that to the `members` list.

This is easily obtained (with the ID as a link, even) by clicking the
"Copy ID and summary to clipboard" icon beside a YouTrack issue's ID
link, near the top-left of the page when viewing an issue in a
sufficiently-wide browser window.

This helps reduce the complexity of the `User->fields()` method, which
was getting overly complicated.

…uest-template

Refine ID Broker's pull-request template

…oups-external-field

[IDP-1176] Add `groups_external` field to User

…oups-external-field-part-2

[IDP-1176] Add `groups_external` field, part 2 (cleanup)

…-groups-external

[IDP-1182] Add endpoint for updating `groups_external`