Resource generator: many-to-many, views, no-PK tables, and prompt UX

[weljoda]

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• Bug fixes include regression tests
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This PR improves mix ash_postgres.gen.resources adding many_to_many detection, views and better conflict resolution. See: https://discordapp.com/channels/711271361523351632/1495458363960721629

I also set up an example project with a legacy DB schema, to test the generator on a real-world schema. https://github.com/weljoda/gen_resources_example

New capabilities

• many_to_many detection. When a table is a pure join table (two FKs to two distinct tables, identity backed by either a composite primary key or a unique index over both FK columns), the generator now emits a many_to_many on each endpoint alongside the has_many to the join resource.
• PostgreSQL VIEW / MATERIALIZED VIEW support via --include-views. View-backed resources are emitted with migrate? false and a :read-only default action. The underlying introspection queries were ported from information_schema to pg_catalog so views are discoverable at all.
• Tables without a primary key are now generated with require_primary_key? false and a :read, create: :* default action, each carrying a # WARNING: comment pointing the user at the fix.
• --skip-many-to-many flag for users who prefer just has_many on join tables.

Conflict-resolution UX overhaul

When multiple FKs produce duplicate default relationship names, the generator now:

• Shows full conflict context (resource, type, destination, FK column, constraint name) and a suggests an alternative name when common naming patterns are detected.
• Offers a menu with the following options: use suggested, auto-resolve remaining on this resource, skip this relationship.
• Tracks a [seen/total] progress counter so you know how many prompts are left per resource.
• Resolves names against existing attributes and previously named relationships, recursing until no collisions remain.

In my usecase this reduced the prompts by using auto-resolve to 4 from 58 previously.

Bug fixes folded in

• opts[:yes] was being checked as opts[:yes?], so --yes never actually short-circuited the conflict prompts. Fixed.
• add_primary_key/2 was called with a boolean instead of the attribute struct, so its pattern match never fired and composite-PK join tables. Previously the compiler raised an error when generating resources with composite-PK join tables.

Generated-code ordering

• relationships do now groups by type (belongs_to → has_one → has_many → many_to_many) then alphabetical within each group, instead of all-alphabetical with many_to_many interspersed.
• references do is alphabetical by relationship name, matching the belongs_to order rather than FK-insertion order.

[zachdaniel]

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