Adding pinned dependencies in constraint file

Below are the rules for the format when adding any pinned dependency in the file

• Add the date the constraint was added to see at-a-glance how old certain pins are.

• Add headers like "Date:", "Description:", and "Ticket:" to make the format more official, and easier to duplicate.

• Add a link to a github issue for unpinning each constraint.

  • Create tickets as-needed.

  • Add details to ticket to allow constraint description to be brief.

  • Exceptions, like edx-enterprise, might use something like Ticket: N/A (Updated as needed.)

• Alphabetically sort constraints. We used to do this. It makes them simpler to find, and makes it less likely we'll have duplicate constraints. Related constraints can use the same ticket or the description can refer to another constraint.

• Ensure a new line before/after each separate constraint. This is mostly complete.