* add api route for validating a dashboard json
* add feature flag for showDashboardValidationWarnings
* tidy up
* comments and messages
* swagger specs
* fix typo
* more swagger
* tests!
* tidy test a little bit
* no more ioutil
* api will return different status code depending on validation error
* clean up
* handle 4xx errors
* remove console.log
* fix backend tests
* tidy up
* Swagger: Exclude alpha endpoints
Co-authored-by: Sofia Papagiannaki <1632407+papagian@users.noreply.github.com>