get_autocrypt_headers

Creates a new AutocryptHeaderList of relevant headers of the given type based on the addresses of an this.

Each header in the returned list will:

• have a valid address
• be of the type requested
• be complete

If no Autocrypt header is found for an address, no AutocryptHeader will be in the list associated with that e-mail address.

Note that the following types of Autocrypt headers will not be returned by this function:

• headers of an unrequested type
• headers that do not match an address in "From:"
• unparseable headers
• headers with unknown critical attributes
• duplicate valid headers for a given address

On error (e.g. if this version of GMime cannot handle the requested Autocrypt type, or if a parameter is missing or malformed), returns null

The returned Autocrypt headers will have it effective_date set to effective_date

if keep_incomplete isn't set, incompletes are removed

Parameters:

this	a Object
effective_date	a DateTime object
matchheader	the header we want to match
addresses	a InternetAddressList
keep_incomplete	true if the we should include incompletes

Returns:

a new AutocryptHeaderList object, or null on error.