Introduce ADR for fingerprinting

[jazairi]

Overview of changes

Why these changes are being introduced:

We currently use fingerprinting for suggested resources. We are planning to expand this functionality to terms to support clustering, and we also need to refactor suggested resource fingerprinting to accommodate multiple phrases/fingerprints per suggested resource. This felt like a good opportunity to reevaluate our fingerprinting implementation.

Relevant ticket(s):

• TCO-74
• Add automatic fingerprinting for Term records (unticketed -- link to PR)

How this addresses that need:

This ADR proposes that we add a central Fingerprint model, linked to Terms, which is leveraged by SuggestedResource and any other detectors that require fingerprinting.

EngX had discussed this as a possible approach in a recent meeting. Consensus on this ADR would confirm the decision.

Side effects of this change:

See ADR for details.

Developer

Ticket(s)

See above.

Accessibility

• ANDI or Wave has been run in accordance to our guide and
  all issues introduced by these changes have been resolved or opened
  as new issues (link to those issues in the Pull Request details above)
• There are no accessibility implications to this change

Documentation

• Project documentation has been updated, and yard output previewed
• No documentation changes are needed

ENV

• All new ENV is documented in README.
• All new ENV has been added to Heroku Pipeline, Staging and Prod.
• [z] ENV has not changed.

Stakeholders

• Stakeholder approval has been confirmed
• Stakeholder approval is not needed

Dependencies and migrations

NO dependencies are updated

NO migrations are included

Reviewer

Code

• I have confirmed that the code works as intended.
• Any CodeClimate issues have been fixed or confirmed as
  added technical debt.

Documentation

• The commit message is clear and follows our guidelines
  (not just this pull request message).
• The documentation has been updated or is unnecessary.
• New dependencies are appropriate or there were no changes.

Testing

• There are appropriate tests covering any new functionality.
• No additional test coverage is required.

[matt-bernhardt]

Thanks for your patience while I think this through. I agree with this decision; I don't have a meaningful addition to the options, and the only other contributions I've come up with in reading this have felt more nits than substance.