domains: creating new domain fails if flagged is not set

[zzacharo]

Package version (if known): v12.0.0b3.x

Describe the bug

When creating a domain via the administration panel, the "Flagged" checkbox must be clicked otherwise it leads to validation error.

Expected behavior

The checkbox is not required, thus it should be able to omit ticking it. Moreover, the required properties seem to be more than the "Domain" input. This needs to be verified and adapt the UI accordingly e.g add red asterisks to the corresponding fields.

Screenshots (if applicable)