Certificate validity checking

[uhurusurfa]

Provide ability to have the validity of the configured certificates checked periodically.
The check should have a warning feature that can send an email or other notification to facilitate early exchange a new certificate with the AS2 partner before the validity expires.

Implementation:

1. if the certificate is still valid for 30 days, an info/warning will be displayed in the log.
2. if the certificate has expired, an error will be displayed in the log.
3. provide an email mechanism to notify when certicate is expiring or has expired
4. enabled and configurable in config.xml

Possibly incorporate issue #98 into this development.

[VboxNick]

Hi @uhurusurfa,
Some thoughts on this. Let's try to think from operations point of view... How convenient would it be to listen for a warning or a keyword in a log? Would it be easy to use an open HTTP endpoint? The endpoint will return a list warnings and related entities. For security reasons I would expose only fingerprints and some generic messages. Any monitoring system can consume something like this.

[uhurusurfa]

There is the helathcheck endpoint that can be used for this if you are thinking in terms of a monitoring system that polls OpenAS2 for issues.
Currently it is fairly simple in terms of the response but can be enhanced to provide whatever an external monitoring system would need. It could even be enhanced to provide pluggable formatters for responses.