fix: passing did document in options

[vmidyllic]

This pull request introduces support for passing and handling the sender's DID Document throughout the authentication flow in the auth.ts handler. The changes ensure that the sender's DID Document can be provided as an option, propagated through relevant types and methods, and included in the authentication response body.

Enhancements to DID Document handling:

• Added DIDDocument to the imports from ../types in auth.ts to enable usage of the type throughout the file.
• Extended the AuthReqOptions and AuthHandlerOptions types to include an optional senderDIDDocument property, allowing the sender's DID Document to be passed into authentication operations. [1] [2]
• Updated the AuthHandler class to include the senderDIDDocument in the authentication response body under the did_doc field, ensuring it is returned as part of the response.
• Modified the call to handleAuthRequest to propagate the senderDIDDocument option, ensuring it is available during request handling.