custom webhooks and other webhook modifications

[audibleblink]

Currently, there is no implementation that is specific to Slack Webhooks, so this PR makes it more obvious that it's just POSTing to a URL with the pre-determined JSON template of {"text": "..."}.

Also, INFO felt too low for a notification-worthy log level on slack/mattermost/etc.

The resulting notification had ANSI color characters, making it hard to read, so those were stripped as well. ( #30 )

• raises loglevel threshold for webhook notifications
• remove ANSI color codes from HTTP payloads for cleaner notifications
• modify docs/code to reflect generic capabilities of webhooks

[eth0izzle]

Thanks @audibleblink.

Do you think we need a setting for the JSON template? i.e. webhook_message_format: "{'text': '%s'}" in config.yaml. And do most webhooks work with {"text": "..."}? i.e. Discord as mentioned in #29.

[audibleblink]

I looked at Discord and it has a few more requirements, but having the ability to define the JSON payload in the config would allow the most flexibility.

I'd be down with adding that config option.

[audibleblink]

Alright @eth0izzle, got this working with the template string in config.yaml.

For testing with Discord, this might be useful: https://discord.com/developers/docs/resources/webhook#execute-webhook

I believe one would just need to change text to content in the config.yml

Wanna give it a shot @CyberSecGuy?

[audibleblink]

Spun one up and tried.

config.yml entry

webhook_payload: |
  {
    "content": "%s"
  }

[eth0izzle]

Thanks @audibleblink