DoD

• GetSettings and ChangeSettings APIs work with AlertManager configuration.

Implementation

• Add AlertManager address (a single string) to Settings.
• Expand ChangeSettings API to set (string) or remove (boolean flag) AlertManager address, and to set (a string with content) or remove (boolean flag) rules file.
• Expand GetSettings API to return those values.
• Put this file into a temporary location and check it with promtool. If it's ok, put a file on the filesystem in a fixed location /srv/prometheus/rules/pmm.rules.yml (that path is already added to prometheus.yml generator) and reload Prometheus.
• Try to chmod this file. If it fails, log error and continue.
• Do not store rules in the database.

Discussion

• We don't have "upload file" fields.