Support for compatibility versioning

[austindrenski]

Opening to track discussions about compatibility versioning.

Proposed

• Update the docs to better describe how we support different versions:
  • Migrations
  • SQL generation
  • Type mapping
• Add support to target a specific backend.
  • PostgreSQL (default)
  • Amazon Redshift
  • CockroachDB
  • CrateDB
• Add support to target a specific backend version.
  • Introduced in Add support for backend compatibility #483.
• Analyze compatibility for existing function and operator translations:
  • Arrays
  • NpgsqlNetworkTranslator
  • NpgsqlDateAddTranslator
  • NpgsqlDateTimeMemberTranslator
  • NpgsqlRangeTranslator

Related:

• Amazon Redshift support #260
• Npgsql.EntityFrameworkCore.PostgreSQL generates unsupported sql for old postgresql server #478