Allow to block providers by name, not only by ID

[krassowski]

Problem

• I want to allow-list 3 providers and nothing more
• I want jupyter server to start up quickly
• but currently an attempt to import each and every provider will be made because the checks for whether provider is allowed are only done after it is loaded

Proposed Solution

Make it possible to allow-list and block-list based on entry point name rather than on provider ID?

jupyter-ai/packages/jupyter-ai-magics/jupyter_ai_magics/utils.py

Lines 66 to 76 in 53251f6

	try:
	provider = model_provider_ep.load()
	except Exception as e:
	log.info(
	f"Unable to load embeddings model provider class from entry point `{model_provider_ep.name}`: %s.",
	e,
	)
	continue
	if not is_provider_allowed(provider.id, restrictions):
	log.info(f"Skipping blocked provider `{provider.id}`.")
	continue

Like AiExtension.allowed_provider_entry_points or AiExtension.allowed_provider_names?

Additional context

Somewhat related annoyances:

• Error log when starting up extension #839
• Slow and blocking startup of jupyter-ai server extension #1115

[dlqqq]

@krassowski Thank you for this detailed proposal! I agree the startup time is an issue. I think we should also explore if there's a backward-compatible way of reducing the startup time, without requiring users specify a configurable trait that blocks entry points. Let's continue the discussion in #1115.