Previously, commit e5d2e95 attempted to change the styling of the user
profile pill containers to match the inputs above it. However, it used
an incorrect selector (#settings_page), resulting in all other pill
containers on settings pages being changed to match it as well
(example: User groups pill containers in Organization
settings). Additionally, its selector's specified background attribute
resulted in problems in dark mode.
To correctly style the user profile pill containers to match the other
input's styling, we apply the uneditable-input class native to
Bootstrap so that we don't need to create an entirely new selector to
style it.
Note that the .custom_user_field .pill-container selector was added so
that it could match the padding of inputs. Also, the
.custom_user_field .pill-container:focus-within selector was added
with attributes straight from Bootstrap's input:focus selectors so
that .custom_user_field .pill-container would have a blue outline
while users were typing in the input pill, just like the other inputs.
This makes a few important cleanup changes:
* Using the more standard data-field-id name for the ID value.
* Using $(e.target).closest() rather than `.parent`, which is more
robust to future changes in markup.