stateless tipg: remove `collection_catalog`

[vincentsarago]

Since the start of tifeature/timvt/tipg, we designed the application with having a list of the available collections/layers stored in the application State:

tipg/tipg/db.py

Line 83 in 489f024

app.state.collection_catalog = await get_collection_index(app.state.pool, **kwargs)

This gave some advantages:

• cost of running the collection listing is only paid once (at startup)
• we know what are the available collection so we can raise useful error if the user input collection is not in the list

  tipg/tipg/dependencies.py

  Lines 40 to 43 in 489f024

  	collection_catalog = getattr(request.app.state, "collection_catalog", {})
  	if collectionId in collection_catalog:
  	return collection_catalog[collectionId]

• cheap collection filtering https://github.com/developmentseed/tipg/blob/main/tipg/factory.py#L439-L458

The collection_catalog is created at application startup

tipg/tipg/main.py

Lines 65 to 80 in 489f024

	@app.on_event("startup")
	async def startup_event() -> None:
	"""Connect to database on startup."""
	await connect_to_db(app, settings=postgres_settings)
	await register_collection_catalog(
	app,
	schemas=db_settings.schemas,
	exclude_schemas=db_settings.exclude_schemas,
	tables=db_settings.tables,
	exclude_tables=db_settings.exclude_tables,
	function_schemas=db_settings.function_schemas,
	exclude_function_schemas=db_settings.exclude_function_schemas,
	functions=db_settings.functions,
	exclude_functions=db_settings.exclude_functions,
	spatial=db_settings.only_spatial_tables,
	)

because we assumed it's a pretty costly process.

The problem then (as explained in developmentseed/eoAPI#55 (comment)) is when you have changed in the DB (e.g new table) it won't show up in the application because the catalog is now updated.

Proposal

• remove collection_catalog
• create a clean SQL function which will list the collections
• the function should accept id (to return only one collection), limit, offset, spatial_filter and temporal_filter

cc @bitner

[bitner]

We will also need to take into account merging in the overrides that can come from environment variables.

I will note, that we can use the existing function right now to filter by collection by setting tables= and functions=.