at_activate error message for duplicate enrollments could be more helpful

[cpswan]

Describe the bug

If I try to perform an enrollment using the same --drx parameter as before then the error message doesn't really explain what's wrong.

[INFO] 2025-02-05 11:07:13.294357 | connection | Connected
[ERROR] 2025-02-05 11:07:14.323532 | atauth_enroll_response | Did not receive data response from enroll request
[ERROR] 2025-02-05 11:07:14.323580 | ENROLL | atauth_send_enroll_request: 1

Steps to reproduce

1. First I enroll an atSign using at_activate enroll -a ${atsign} -s ${otp} -p noports -k ${home}/.atsign/keys/${atsign}_key.atKeys -d ${device} -n "sshnp:rw,sshrvd:rw"
2. Then I try another enrollment with exactly the same parameters.

Expected behavior

An error message that states an enrollment already exists for that DeviceName (which could go on to suggest that if you need to recreate an APKAM key for a device then it should be revoked and then re-enrolled).