What should be done?

We should allow uppercase Latin letters in a way that the backend supports it. For example, it should be possible to create database ABC with PostgreSQL backend, but then it will be the same as abc, aBc, etc.

Where?

• FerretDB/internal/handlers/pg/pgdb/databases.go

  Lines 30 to 31 in cc34dfc

  	// validateDatabaseNameRe validates FerretDB database / PostgreSQL schema names.
  	var validateDatabaseNameRe = regexp.MustCompile("^[a-z_-][a-z0-9_-]{0,62}$")

• FerretDB/internal/util/testutil/db.go

  Lines 66 to 67 in cc34dfc

  	// database names are always lowercase
  	name := strings.ToLower(tb.Name())

• FerretDB/website/docs/diff.md

  Line 29 in cc34dfc

  * database name cannot contain capital letters;

Definition of Done

• pgdb tests updated;
• integration/compatibility tests updated;
• user documentation updated.