feat: support declarative schema with db diff

[sweatybridge]

What kind of change does this PR introduce?

closes https://github.com/supabase/cli/issues/1215

What is the new behavior?

• Add schema files to supabase/schemas (they will be run in lexical order)
  • Easiest way to create one is supabase db dump --local -f supabase/schemas/base.sql
• Then run supabase db diff

A new local database will be created from declared schemas for diffing.

$ supabase db diff
Creating local database from supabase/schemas...
Setting up initial schema...
Creating custom roles supabase/roles.sql...
Applying schema supabase/schemas/base.sql...
Connecting to local database...
Creating shadow database...
Setting up initial schema...
Creating custom roles supabase/roles.sql...
Applying migration 20231204107450_grant.sql...
Diffing schemas: extensions,private,public
Finished supabase db diff on branch dec-schema.

No schema changes found

Additional context

Add any other context or screenshots.

[coveralls]

Pull Request Test Coverage Report for Build 8933882059

Details

• 11 of 64 (17.19%) changed or added relevant lines in 6 files are covered.
• 5 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.3%) to 57.48%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/db/diff/pgadmin.go	0	1	0.0%
internal/utils/flags/db_url.go	0	1	0.0%
internal/db/diff/diff.go	6	57	10.53%
<!--	Total:	11	64

Files with Coverage Reduction	New Missed Lines	%
internal/gen/keys/keys.go	5	11.76%
<!--	Total:	5

Totals
Change from base Build 8933751783:	-0.3%
Covered Lines:	6386
Relevant Lines:	11110

---

💛 - Coveralls

[xleddyl]

@SweatyBridge I tried creating a supabase/schemas folder and putting the definitions inside, but I can't manage to make the script work. It always diffs the local DB with the one generated from the migrations and not the schema.

Can you check if this still works or has been deprecated?