contains_message_info_data

Description:

public bool contains_message_info_data (Folder folder, string orig_message_uid)

Returns whether data_cache contains given orig_message_uid for the given folder.

Unlike get_message_info_data, this only returns false if not, while get_message_info_data auto-adds it to data_cache.

this	a VeeDataCache
folder	a Folder to which the `orig_message_uid` belongs
orig_message_uid	a message UID from the `folder` to check