feat: datasource for supabase_project_apikeys

[gabornyergesX]

What kind of change does this PR introduce?

This PR introduces a new data source supabase_project_apikeys that allows retrieving API keys for a Supabase project. This is a read-only data source that provides access to both the anonymous and service role API keys.

What is the current behavior?

Currently, there is no way to programmatically retrieve Supabase project API keys using Terraform. Users need to manually copy these values from the Supabase dashboard or store them separately.

What is the new behavior?

The new data source allows users to:

• Retrieve both anon and service role API keys for a specified project
• Reference these keys securely in other Terraform resources
• Automatically handle sensitive values with proper marking in Terraform state

Example usage:

data "supabase_project_apikeys" "example" {
  project_id = "abcdef123456"
}

# Use the keys in other resources
resource "some_resource" "example" {
  api_key = data.supabase_project_apikeys.example.anon_key
}

[sweatybridge]

Thank you for contributing this change! closes #71

[gabornyergesX]

i fixed the tests.