Add policy Enforce tag Name and Value casing on resource groups and subscriptions

[mitramcc]

Policy that will update the case of Tag Names and values for a specific Tag Name

[donk-msft]

Tested policy on subscription and resource group level.
Works as expected. When parameter 'applyCaseToValue' is 'true', both tag name and value are converted to either upper- or lowercase. When 'applyCaseToValue' is 'false' it only converts the tag name.

[donk-msft]

Policy Name (4c79587a-c4a1-5c28-8806-d7d29d3c114c) does not conflict with existing policy names.