Add Panther Plugin Framework

[adammcdonagh]

Draft PR looking for any comments before submitting.

The primary purpose of this PR is to add a mechanism to extend Panther with custom plugins that impact the core functionality. This includes adding SSO, editing the alert schema with custom columns, injecting actions into the insert/update/delete events.

SSO has been tested and validated with Google SAML auth - See https://github.com/adammcdonagh/panther-sso-saml
Example plugin for adding custom columns to the schema can be found here - https://github.com/adammcdonagh/panther-custom-columns

Changes

• Console startup now loads configured plugins and lets them run applyConsole(...).
• Console startup also exposes auth helpers so plugins can register SSO providers and disable built-in local auth before Express boot. (currently untested)
• A second hook, applyConsoleAuth(...), runs after Express creation so plugins can register Passport strategies and auth routes. (currently untested)
• Plugins can register admin sections, which are rendered into the admin page.
• Login views now render configured auth providers, and POST /login falls through when local auth is disabled so a plugin can own that path. (currently untested)
• Console config now has a first-class auth section with local.enabled and providers defaults.
• Console config now allows a plugins section.
• Field.extend(...) lets plugins add field definitions/default visible fields.
• Server startup now loads configured plugins and runs applyServer(...) before alert schema registration.
• The alert loader can now append column definitions, create indexes, and backfill defaults for new columns.
• Container entrypoints can now perform runtime plugin installs for stock images using PANTHER_PLUGIN_INSTALL and PANTHER_PLUGIN_DIR.
• Repository docs now describe the generic plugin contract, recommended naming, source-build flow, and stock-image runtime install flow.
• Modified some of the Docker build scripts to allow full local builds using Docker, and include new plugin loading mechanism when plugins are hosted on public Git repos.

[vinceoa]

Hi Adam,
Welcome to the Panther project and thank you for the very first PR.

There are a few suggestions and alterations that would make merging this easier, generally along the lines of splitting it up into smaller reviewable chunks:

• OA_CONFIG_FILE renaming, having that on its own would help us align our internal builds.
• Core plugin framework, this being more targeted would make it easier to review on its own.
• Alert schema extensions, looks handy, there is an existing (albeit simple) migration setup using migrate-mongo, this would be the preferred route for schema changes at present. (from within the event-server's entrypoint)

Things we'd decline right now:

• SSO login changes. We are looking at providing this in the future as part of a gated feature.
• Docker container runtime setup, npm install / git clone'ing should be kept out of runtime, it makes it harder to run the security scanners as deps are not known ahead of time.