When package name is empty, but type_path is filled, the fq_message_name should begin with a single dot.
Two duplicate implementations are moved to a separate function.
A test is added that creates a sub message without a package name. The code generator uses the message name to generate a rust module path, which is invalid.
When package name is empty, but type_path is filled, the fq_message_name should begin with a single dot.
Two duplicate implementations are moved to a separate function.
A test is added that creates a sub message without a package name. The code generator uses the message name to generate a rust module path, which is invalid.
fixes: #843