If you define challenge handlers on a per-domain basis multiple will be
created. This would cause the standalone handler to potientially try
to bind the same port (when configured) multiple times, which would only
work on the first try. Subsequent tries would fail with "Address already
in use". To fix this only bind the server between start and stop of the
challenge and cleanup afterwards.
This simple implementation writes log messages to stdout/err and flushes
the buffers immediately after the message has been written.
Also update log messages with the certificate CN to a better readable format
Introduce functions for get_cert_cn and get_cert_valid_until to
encapsulate all cryptographic functions consistently in tools.
- Remove wait times returned by create_challenge
- Remove wait loops from authorities
- Add the wait for valid DNS TXT records in the abstract
DNSChallengeHandler start_challenge function.
- Move challenge verification to start_challenge in general
