The arm selecting the Mongo adapter over the native mongodb driver.
options.url is required by the union unless options.client is supplied,
so a registration that forgets both is a compile error instead of a
connect() throw — the same guarantee the 'custom' arm gives
adapter. The client is supplied inject-or-lazy (§12.2 of AI_GUIDELINES):
client is an already-constructed structural IMongoClient, and absent it
the adapter performs a literal import('npm:mongodb@^6.21.0') at connect time.
readonly
type: "mongodb"
Selects the Mongo arm.
readonly
options: MongoAdapterOptions
Mongo adapter configuration; url (or client) is required.