Create a Hook that overrides languages with the following hierarchy (and keys)
(where XX is a locale like 'it')
When requesting the 'key1' for the locale XX the returned value is from Language-ext.properties.
The expected behavior is to read the value for the key1 in Language_XX.properties file.
The problem is that the current logic merges the two files for the default locale and then for each XX file, it first merges the file with the default keys and then replaces the existing keys for that locale. The result in our case is that when Language-ext_XX.properties is processed, key1 from Language_XX.properties will be overwritten with key1 from the default files.