* FEATURE: allow plugins and themes to extend the default CSP
For plugins:
```
extend_content_security_policy(
script_src: ['https://domain.com/script.js', 'https://your-cdn.com/'],
style_src: ['https://domain.com/style.css']
)
```
For themes and components:
```
extend_content_security_policy:
type: list
default: "script_src:https://domain.com/|style_src:https://domain.com"
```
* clear CSP base url before each test
we have a test that stubs `Rails.env.development?` to true
* Only allow extending directives that core includes, for now
At the moment core providers are hard-coded in Javascript, and plugin providers get added to the JS payload at compile time. This refactor means that we only ship enabled providers to the client.
Kyle Zhao
David Taylor
Gerhard Schlager
Guo Xiang Tan
Sam