Introduce "status" field into Provider class

[cthoyt]

          Agreed, I think introducing a controlled vocabulary for "status" in the Provider class would accomplish this - then we could flag things as being "legacy" URLs that either still can be resolved or not.

Originally posted by @cthoyt in #1386 (comment)

This can be implemented using either an optional Literal or as an enumeration within the following Pydantic model:

bioregistry/src/bioregistry/schema/struct.py

Lines 246 to 264 in 39ba3f9

	class Provider(BaseModel):
	"""A provider."""
	code: str = Field(..., description="A locally unique code within the prefix for the provider")
	name: str = Field(..., description="Name of the provider")
	description: str = Field(..., description="Description of the provider")
	homepage: str = Field(..., description="Homepage of the provider")
	uri_format: str = Field(
	...,
	title="URI Format",
	description=f"The URI format string, which must have at least one ``$1`` in it. {URI_IRI_INFO}",
	)
	first_party: Optional[bool] = Field(
	None, description="Annotates whether a provider is from the first-party organization"
	)
	publications: Optional[List["Publication"]] = Field(
	default=None,
	description="A list of publications about the provider. See the `indra` provider for `hgnc` for an example.",
	)