Connector helpers to obtain INDEX and FOREIGN KEY configurations from model definitions

[bajtos]

This is a follow-up task for the proposal outlined in https://github.com/strongloop/loopback-next/issues/2712.

Implement a helper functions in base Connector class to process index and foreign-key definitions in an unified way and convert them into data suitable for consumption by connector implementations. The helpers should gather both model-level and property-level definitions, apply database/connector-specific options, merge keys/properties fields in index definitions, etc. and produce a final definition that can be directly mapped to database commands.

See _SPIKE_.md in https://github.com/strongloop/loopback-next/pull/2712 for the full description of index/PK definition syntax.

This is a prerequisite for implementation of indexes & foreign keys in other connectors, most notably memory connector (https://github.com/strongloop/loopback-next/issues/2333) and SqlConnector (https://github.com/strongloop/loopback-connector-rest/issues/135)

Acceptance criteria

• [ ] Implement a helper to process INDEX definitions, include tests and API docs
• [ ] Implement a helper to process FOREIGN KEY definitions, include tests and API docs
• [ ] Deprecate ModelDefinition.prototype.indexes() API in favor of this new Connector method.
• Create follow-up tasks to leverage the new helper in our NoSQL connectors and thus let the connectors understand the new FK/INDEX definition syntax. One GH issue per connector please.
  • [ ] MongoDB
  • [ ] CouchDB
  • [ ] Cloudant
  • [ ] Cassandra

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.