When allow_embedding is false (default) the Grafana backend
will set the http header `X-Frame-Options: deny` in all responses
to non-static content which will instruct browser to not allow
Grafana to be embedded in `<frame>`, `<iframe>`,
`<embed>` or `<object>`.
Closes#14189
* Store passwords in secureJsonData
* Revert unnecessary refactors
* Fix for nil jsonSecureData value
* Remove copied encryption code from migration
* Fix wrong field reference
* Remove migration and provisioning changes
* Use password getters in datasource proxy
* Refactor password handling in datasource configs
* Add provisioning warnings
* Update documentation
* Remove migration command, moved to separate PR
* Remove unused code
* Set the upgrade version
* Remove unused code
* Remove double reference
