Explore: Add transformations to correlation data links (#61799)

* bring in source from database

* bring in transformations from database

* add regex transformations to scopevar

* Consolidate types, add better example, cleanup

* Add var only if match

* Change ScopedVar to not require text, do not leak transformation-made variables between links

* Add mappings and start implementing logfmt

* Add mappings and start implementing logfmt

* Remove mappings, turn off global regex

* Add example yaml and omit transformations if empty

* Fix the yaml

* Add logfmt transformation

* Cleanup transformations and yaml

* add transformation field to FE types and use it, safeStringify logfmt values

* Add tests, only safe stringify if non-string, fix bug with safe stringify where it would return empty string with false value

* Add test for transformation field

* Do not add null transformations object

* Break out transformation logic, add tests to backend code

* Fix lint errors I understand 😅

* Fix the backend lint error

* Remove unnecessary code and mark new Transformations object as internal

* Add support for named capture groups

* Remove type assertion

* Remove variable name from transformation

* Add test for overriding regexes

* Add back variable name field, but change to mapValue

* fix go api test

* Change transformation types to enum, add better provisioning checks for bad type name and format

* Check for expression with regex transformations

pkg/services/provisioning/datasources/datasources.go

@@ -152,6 +152,10 @@ func makeCreateCorrelationCommand(correlation map[string]interface{}, SourceUID
 		createCommand.TargetUID = &targetUID
 	}
 
+	if correlation["transformations"] != nil {
+		return correlations.CreateCorrelationCommand{}, correlations.ErrTransformationNotNested
+	}
+
 	if correlation["config"] != nil {
 		jsonbody, err := json.Marshal(correlation["config"])
 		if err != nil {