Generating stricter dependencies on python3-protobuf rdeps

[Adrian Bunk <bunk@debian.org>]

Hi,

the problem in #1031716/#1028371 is as follows:

1. python3-protobuf and protobuf-compiler are both built from
   src:protobuf

2. packages using python3-protobuf (e.g. python3-bernhard) ship files 
   that were generated with protobuf-compiler during their build
   (e.g. /usr/lib/python3/dist-packages/bernhard/pb.py )

3. The generated files in python3-protobuf rdeps like python3-bernhard
   might not work with python3-protobuf from a different major release
   of src:protobuf

The manual solution for packages like python3-bernhard would be
Build-Depends: protobuf-compiler (>= 3.21), protobuf-compiler (<< 3.22),
               python3-protobuf (>= 3.21), python3-protobuf (<< 3.22),
Depends: python3-protobuf (>= 3.21), python3-protobuf (<< 3.22),

Creating an own debhelper addon similar to dh_numpy3 would work for 
automatically creating such dependencies, but is there any way for
python3-protobuf to inject such versioned runtime dependencies into
python3:Depends that does not require every rdep to manually add
addon usage?

Thanks
Adrian