TransimisionBase should allow other types than String for Metadata value #96
Description
The following field has the metadata set at a Map<String, String>, however it should be <String, Object> so that when converted to JSON, string, int and boolean should be all be valid values, just like in the other SparkPost clients.
@Description(
value = "Transmission level metadata containing key/value pairs. Metadata is available during events through the Webhooks and is provided to the substitution engine. A maximum of 1000 bytes of merged metadata (transmission level + recipient level) is available with recipient metadata taking precedence over transmission metadata when there are conflicts.",
sample = {""})
private Map<String, String> metadata = null;