EnsureAcmeChallengeFormat takes a domain name as a string, tests if it already has the acme-challenge format, and appends any missing substrings to ensure the acme challenge format.

ValidateAcmeChallengeInput checks if the ACME challenge provided conforms to the ACME challenge format.

ValidateDomainName checks if the parameter 'domain' is a valid domain name.

ValidateDomainNameWildcard checks if the parameter 'domain' is a valid domain name including the wildcard character used in wildcard certificates as the Common Name (CN) or Subject Alternative Name (SAN).

The ResolveTester can be used to test if a set DNS01 acme challenge has been actually placed on a DNS service so it can be successfully validated.