error generating migration

[kingshalaby1]

Describe the bug
I got an error when I tried to generate a migration after I modified an existing resource attributes

MIX_ENV=test mix ash_postgres.generate_migrations --apis AshPostgres.Test.Api

I get this error:

** (SyntaxError) nofile:18: unexpected token: ":" (column 17, code point U+003A)
    (elixir 1.10.4) lib/code.ex:654: Code.format_string!/2
    lib/migration_generator/migration_generator.ex:332: AshPostgres.MigrationGenerator.write_migration/4
    (elixir 1.10.4) lib/enum.ex:789: anonymous fn/3 in Enum.each/2
    (stdlib 3.12.1) maps.erl:232: :maps.fold_1/3
    (elixir 1.10.4) lib/enum.ex:2127: Enum.each/2
    (mix 1.10.4) lib/mix/task.ex:330: Mix.Task.run_task/3
    (mix 1.10.4) lib/mix/cli.ex:82: Mix.CLI.run_task/2.

To Reproduce

1. add a new attribute new_field to an existing resource Post in test/support/resources/posts.ex
2. generate a migration using ash_postgres.generate_migrations task

Expected behavior
it should create a new migration file to alter table :posts, adding column :new_field correctly

** Runtime

• Elixir 1.10.4
• Erlang/OTP 22
• Ash version 1.19
• postgres (PostgreSQL) 12.2

[zachdaniel]

Fixed in #25