Provisioning: Allow saving of provisioned dashboards

[jongyllen]

What this PR does / why we need it:
Allows saving of provisioned dashboards if the config value allowUiUpdates is set to true

This lets the user modify and save a dashboard that has been provisioned. It also enables some automation scenarios where the updated dashboards are pulled out via API calls and updated - provisioned to other instances etc.

Which issue(s) this PR fixes:
#11778
Allow UI to save changes for provisioned dashboards

Fixes #11778

Special notes for your reviewer:
Note that if updated on disk - the manually updated dashboard will be overwritten again by the provisioning engine. I recommend creating a separate Issue for this as it requires some thought around behaviour.

I would like the code to be a bit more readable an efficient but I could not find a way of doing that that would not require a big refactor of the services. If there are nice way of cleaning it up a bit, please give me some pointers!

[torkelo]

This looks good.

Just needs some docs.

• What happens when a provisioned dashboard updated in the UI, then later updated in json file
• Is dashboard json version ever taken into account here (when json file is updated after UI save)?
• What happens if json file or provisioned config is removed (and dashboard has an update form UI)?

[marefr]

Looks good 👍 Feels a bit weird to pass the allowUiUpdate flag to the DashboardService, but I understand why it is so and I don't think bringing in the ProvisioningService as a dependency to DashboardService is a good alternative. For now we have to live with the weirdness of the DashboardService that already existed before these changes.

I've added some docs suggestions. Still feel that the docs may need some more thoughts besides my suggestions. Maybe @marcusolsson can help out with this?

[drewhemm]

This is a feature I am watching and eagerly anticipating. If I can be of any assistance in testing etc, please let me know.

I want to be able to hook into the save event somehow and automatically commit a change to the repo where we store our dashboard json.

[gotjosh]

The scope of my review is only limited to the documentation. I'll leave the code part in the very capable hands of @marefr.

[marefr]

LGTM

[jongyllen]

@drewhemm Sure! Feel free to test it and please give feedback if you have any. It will be in the next nightly build.

As for the second part - sounds like an interesting feature, feel free to raise an issue explaining in a little more detail what it should do and what kind of use-cases it would solve.

[torkelo]

Wohoo!