proper error messages on templating screen

[jodok]

if there's an error with the templating sql query, it should be showed properly:

(here's what happened in the background)

• a HTTP 403 error - because a missing CROSS-SITE-ORIGIN header configuration - caused the error

HTTP 403 errors should probably point to the docs that show how to configure it properly

[joemoe]

@alexanderzobnin maybe just return the error message of crate

[alexanderzobnin]

@joemoe Unfortunately, I can't do that because Grafana handle error before I can get it inside plugin code. I just get general error object with odd status -1 and without any explanations. I'll discuss this with @torkelo and we'll try to find better solution.

[joemoe]

ok. i think this would be a good feature as the user then would know what to do.