fix: allow creation of event driven subgraphs

[Noroth]

This pull request introduces support for event-driven subgraphs, refines the handling of subgraph attributes based on their type, and improves protocol resolution logic throughout the codebase. The main changes can be grouped into documentation updates, resource and API logic improvements, and expanded testing.

Support for event-driven subgraphs and improved protocol handling:

Documentation and resource schema updates:

• Updated the documentation and resource schema for cosmo_subgraph to clarify that routing_url is required only for normal subgraphs and optional for event-driven subgraphs. The field is now marked as optional and computed. [1] [2]

Resource and API logic improvements:

• Modified resource creation and update logic so that, for event-driven subgraphs, fields such as routing_url, subscription_url, subscription_protocol, and websocket_subprotocol are omitted from requests and set to null, ensuring correct API usage. [1] [2]
• Refactored protocol resolution functions (ResolveWebsocketSubprotocol, ResolveSubscriptionProtocol) to accept pointer types, allowing for proper handling of optional protocol fields and avoiding default assignments when fields are omitted. Updated all relevant resource and API calls to use the new pointer-based logic. [1] [2] [3] [4] [5] [6]

Testing and validation:

• Added a new acceptance test (TestAccSubgraphEventDrivenSubgraph) and supporting configuration function to validate the creation and management of event-driven subgraphs, ensuring that omitted fields behave as expected. [1] [2]

Schema enhancements for event-driven subgraphs:

• Introduced a comprehensive test schema (TestAccValidEventDrivenSubgraphSchema) with various event-driven directives and types to support robust testing of event-driven subgraph features.

[StarpTech]

LGTM