Create credential request as HolderProver and store in wallet; return credential json and metadata json.

        Raise AbsentLinkSecret if link secret not set.

        :param cred_offer_json: credential offer json
        :param cd_id: credential definition identifier
        :return: cred request json and corresponding metadata json as created and stored in wallet

async def create_cred_req(self, cred_offer_json: str, cd_id: str) -> (str, str):
        """
        Create credential request as HolderProver and store in wallet; return credential json and metadata json.

        Raise AbsentLinkSecret if link secret not set.

        :param cred_offer_json: credential offer json
        :param cd_id: credential definition identifier
        :return: cred request json and corresponding metadata json as created and stored in wallet
        """

        LOGGER.debug('HolderProver.create_cred_req >>> cred_offer_json: %s, cd_id: %s', cred_offer_json, cd_id)

        self._assert_link_secret('create_cred_req')

        # Check that ledger has schema on ledger where cred def expects - in case of pool reset with extant wallet
        cred_def_json = await self.get_cred_def(cd_id)
        schema_seq_no = int(json.loads(cred_def_json)['schemaId'])
        schema_json = await self.get_schema(schema_seq_no)
        schema = json.loads(schema_json)
        if not schema:
            LOGGER.debug(
                'HolderProver.create_cred_req: <!< absent schema@#%s, cred req may be for another ledger',
                schema_seq_no)
            raise AbsentSchema('Absent schema@#{}, cred req may be for another ledger'.format(schema_seq_no))
        (cred_req_json, cred_req_metadata_json) = await anoncreds.prover_create_credential_req(
            self.wallet.handle,
            self.did,
            cred_offer_json,
            cred_def_json,
            self._link_secret)
        rv = (cred_req_json, cred_req_metadata_json)

        LOGGER.debug('HolderProver.create_cred_req <<< %s', rv)
        return rv