Domain names starting with numbers: output helpful error message

[edburns]

I have a customer who tried to create a domain with this domainUID:

domainUID="4cdomain"

The action failed, but without a message indicating the reason being the domainUID value violated this WLS invariant:

Please see #3127 for more details.

[tbarnes-us]

Tracking using internal JIRA OWLS-99865

@rjeberhard @robertpatrick FYI