async getUserDelegationKey(startsOn, expiresOn, options = {}) {
        return tracingClient.withSpan("BlobServiceClient-getUserDelegationKey", options, async (updatedOptions) => {
            const response = assertResponse(await this.serviceContext.getUserDelegationKey({
                startsOn: truncatedISO8061Date(startsOn, false),
                expiresOn: truncatedISO8061Date(expiresOn, false),
            }, {
                abortSignal: options.abortSignal,
                tracingOptions: updatedOptions.tracingOptions,
            }));
            const userDelegationKey = {
                signedObjectId: response.signedObjectId,
                signedTenantId: response.signedTenantId,
                signedStartsOn: new Date(response.signedStartsOn),
                signedExpiresOn: new Date(response.signedExpiresOn),
                signedService: response.signedService,
                signedVersion: response.signedVersion,
                value: response.value,
            };
            const res = Object.assign({ _response: response._response, requestId: response.requestId, clientRequestId: response.clientRequestId, version: response.version, date: response.date, errorCode: response.errorCode }, userDelegationKey);
            return res;
        });
    }
ONLY AVAILABLE WHEN USING BEARER TOKEN AUTHENTICATION (TokenCredential).

Retrieves a user delegation key for the Blob service. This is only a valid operation when using
bearer token authentication.

@see https://learn.microsoft.com/en-us/rest/api/storageservices/get-user-delegation-key

@param startsOn -      The start time for the user delegation SAS. Must be within 7 days of the current time
@param expiresOn -     The end time for the user delegation SAS. Must be within 7 days of the current time