Invalid labels give an unclear error

[adamrtalbot]

If you use an invalid label when launching a pipeline, you get an unclear error:

 ERROR: Name not available

This appears to be directly from the API (using --verbose):

Feb 20, 2025 4:18:11 PM org.glassfish.jersey.logging.LoggingInterceptor log
INFO: 9 * Sending client request on thread main
9 > POST https://cloud.seqera.io/api/labels?workspaceId=280116106690509
9 > Accept: application/json
9 > Authorization: Bearer redacted
9 > Content-Type: application/json
9 > User-Agent: tw/0.11.0 (java)
{"name":"FSN-346","resource":false,"isDefault":false}

Feb 20, 2025 4:18:11 PM org.glassfish.jersey.logging.LoggingInterceptor log
INFO: 9 * Client response received on thread main
9 < 400
9 < Connection: keep-alive
9 < Content-Length: 32
9 < Content-Security-Policy: default-src 'self' 'unsafe-inline' 'unsafe-eval' trim-for-brevity
9 < Content-Type: application/json
9 < Date: Thu, 20 Feb 2025 16:18:11 GMT
9 < Server: nginx
9 < X-Content-Type-Options: nosniff
9 < X-Frame-Options: SAMEORIGIN
9 < X-XSS-Protection: 1; mode=block
{"message":"Name not available"}

If we can, it would be useful to raise an appropriate error and suggest a fix, e.g.:

 ERROR: Label name not available: "FSN-346". Please select something unique.