This constructor can be used to instantiate a fake object. Only used for tests. Any attempt to actually use an object constructed this way will fail as there is no connected Rust object.
Generates an optional UUID to be passed into the string_format method. If the return is not null, then it should be recorded with Glean as a UuidMetricType.
Take the given template and find patterns that match the regular expression {\w+}. Any matches are used as keys into the application context, the additional_context or the special case uuid.