Client allowed sub domains can have spaces

[richardhallett]

Currently when adding sub-domains to a client you can additionally add a space before the subdomain, this causes problems when trying to register a domain as it treats that space as part of the subdomain.

In addition, there is no error message being surfaced about this in Fabrica, in the old MDS UI this would cause a "domain not allowed", however Fabrica accepts the URL but does not actually register it, therefore putting it in a "Findable" state incorrectly.

Reproduce:

1. Add a subdomain to client like "google.com, example.com"
2. Try registering a URL
3. Notice registration doesn't cause an error
4. Notice it's not actually registered

Proposed solution:

1. Strip spaces around sub domains
2. Add errors about invalid domains surfaced in Fabrica

[richardhallett]

Simple fix of just stripping whitespace.