Prior to this commit, the acme service attempted to obtain certificates
once and then terminated, regardless of whether the certificate could be
obtained or not. This commit introduces a new uci option "retries" to
the "certificate" section. If this option is set to N, the acme service
will attempt to obtain the certificate up to N times before terminating.
There is a waiting pause between the retries to comply with the rate
limits of Let'sEncrypt.

The waiting pause is:
-  2 minutes for staging certificates
- 24 minutes for production certificates

The current "Failed Validation" rate limits of Let'sEncrypt are:
- staging:   60 per hour -> 1 failure every 1 minute in avg.
- production: 5 per hour -> 1 failure every 12 minutes in avg.

This means that we are within rate limits by a factor of two.

By default the option "retries" is set to "1", which means that acme
behaves as before by default. If the variable is set to "0", infinite
retries are performed.

This feature is helpful, when you already want to initiate the
certificate request, but you are still waiting for your dns server to be
configured, your network to appear or other conditions.

Signed-off-by: Leonardo Mörlein <git@irrelefant.net>

Before this commit, issue_cert always returned 1 no matter if uacme
returned 1, 2, 3, ... With this commit, the return code of the uacme
binary is propagated. Therefore the caller of issue_cert can
differentiate between "no renew necessary" and "an error occurred".

Signed-off-by: Leonardo Mörlein <me@irrelefant.net>

With this commit, the run-acme script can be included into other scripts
by setting INLCUDE_ONLY=1.

Signed-off-by: Leonardo Mörlein <me@irrelefant.net>

Signed-off-by: Peter Stadler <peter.stadler@student.uibk.ac.at>

Add possibility for user to provide setup and cleanup scripts for
additional flexibility. Setup-script takes precedence over the built-in
behavior of uacme.

This helps users with more complex use-cases to utilize uacme to update
certificates without adding complexity to the provided run.sh script.

Signed-off-by: Antti Seppälä <a.seppala@gmail.com>

lightweight client for the RFC8555 ACMEv2 protocol, written in plain C code
with minimal dependencies (libcurl and one of GnuTLS, OpenSSL or mbedTLS).

Signed-off-by: Lucian Cristian <lucian.cristian@gmail.com>