API changes

• Introduced a new "info" severity for neutral informational messages. These represent messages that may or may not be relevant for certificate issuance - the checker cannot determine this.
• Reduced status.io messages to info severity
• Introduced a new "ok" field in the result JSON. If set to true, the test run was green with no significant problems detected (informational and/or debug problems are likely present, but not relevant for issuance). If set to false, a problem likely affecting issuance was detected.
• Tests older than 7 days are now automatically deleted from the database

Other

• Added prometheus metrics (exposed on /metrics on the profiling service (PPROF_LISTEN_ADDR, default 127.0.0.1:9151)
• Several bugfixes
• Many dependency upgrades

Full Changelog: v1.9.0...v2.0.0

• Add domainExistsChecker
• Add UnexpectedHttpResponse
• Make Makefile build for arm64 (GitHub releases still amd64)
• Minor fixes
• Documentation updates
• Update dependencies