migrations: CREATE IF NOT EXISTS style commands not supported

[olavloite]

Cloud Spanner does not support CREATE IF NOT EXISTS style DDL statements. These are sometimes needed for EF Core migrations.

[mickeldebs]

Hey, any eta on this?

[abbottdev]

This would be great as it would enable the Idempotent migrations feature here: https://learn.microsoft.com/en-us/ef/core/managing-schemas/migrations/applying?tabs=dotnet-core-cli#idempotent-sql-scripts

[abbottdev]

bump: we can't currently use the dotnet ef migrations script command to generate DDL statements for database upgrades