Parse locale for currency lookup with dash separator

Correctly validate Slack field as optional

Closes #2714

Add Finance 1 and Finance 2 Flow

Add django-fsm for invoice status transition

Update to latest django-hijack and remove loading of removed hijack-styles.css

Update to Django 2.2.27.

Update node packages.

Update to django-hijack 3.0.0

Update django-webpack-loader to 1.0.0

Update the image docker is using and the node version to 16.x.

Update to Python runtime 3.9.10.

Do linting directly with npm and stylelint. Lint fixes for scss files.

Updating linting of react code

Fix docker permissions

When the package.json and package-lock.json files are copied they may
not have the proper permissions, which results in a build failure.

By setting the permisssions *after* the copy is performed we ensure
they will be available to npm during `npm install`

Issue #2694