Performer custom fields (#5487)

* Backend changes
* Show custom field values
* Add custom fields table input
* Add custom field filtering
* Add unit tests
* Include custom fields in import/export
* Anonymise performer custom fields
* Move json.Number handler functions to api
* Handle json.Number conversion in api

pkg/utils/map.go

@@ -1,7 +1,6 @@
 package utils
 
 import (
-	"encoding/json"
 	"strings"
 )
 
@@ -80,19 +79,3 @@ func MergeMaps(dest map[string]interface{}, src map[string]interface{}) {
 		dest[k] = v
 	}
 }
-
-// ConvertMapJSONNumbers converts all JSON numbers in a map to either float64 or int64.
-func ConvertMapJSONNumbers(m map[string]interface{}) (ret map[string]interface{}) {
-	ret = make(map[string]interface{})
-	for k, v := range m {
-		if n, ok := v.(json.Number); ok {
-			ret[k] = JSONNumberToNumber(n)
-		} else if mm, ok := v.(map[string]interface{}); ok {
-			ret[k] = ConvertMapJSONNumbers(mm)
-		} else {
-			ret[k] = v
-		}
-	}
-
-	return ret
-}