Added support for Jira, Pagerduty and Increased Slack to include webooks and custom fields

[0xrob]

I've created some Custom alert_action to add additional support for pagerduty and Jira.

I have a feeling these applications are popular enough that this feature would benefit the wider contentctl community.

I've attached some images if you'd like to see a POC.

PagerDuty

Jira

This code can be tested by adding the alert_action key in the yaml file. See below

alert_action:
jira:
account: JiraServiceAccount
jira_attachment: enabled_json
jira_dedup: enabled
jira_dedup_content: your condition
jira_description: your description
jira_issue_type: Alert
jira_priority: Three
jira_priority_dynamic: your dynamic priority
jira_project: your project
jira_summary: your summary
pagerduty:
pagerduty_description: your description
integration_url_override: optional pagerduty url
slack:
channel: your channel
message: your message
fields: outputted fields
webhook_url: webhookurl

This is my first PR with contentctl so let me know what else i need to add or supply.