Its customization hardcoded an empty selector map instead of the one
computed from the options type, so the plural kwarg was rejected. Let
codegen build the options argument for custom facade methods that take
**kwargs.
Vala's default argument is absent from the .gir, so the generated facade
made the port mandatory. Declare the default in the customizations, and
let param_typings override the facade signature also when there is no
custom logic.
The GTlsCertificate-typed properties had no marshaller, so their setters
were never generated. Marshal them to and from a string holding either a
PEM blob or a filename, like the old hand-written bindings did.
Reported and diagnosed by rev1si0n <[email protected]>.