docs: ADR for bulk enrollment endpoint (#1240)
docs: ADR for bulk enrollment endpoint (#1240)

* docs: ADR for bulk enrollment endpoint

* docs: Update with more decision content

Add more content on decisions and consequences

ENT-4233

* docs: reformat a bit, clarify

reformat a bit, clarify

* docs: fix title

fix title

* docs: reformat

reformat

* docs: Fix ups based on feedback

* clarify existing enrollment
edx/edx-enterprise,edx/edx-enterprise,edx/edx-enterprise