feat(pubsub): install pubsub_mocks pkg

[dbolduc]

Part of the work for #5782

• Move google-cloud-cpp::pubsub_mocks out of pubsub-targets and into pubsub_mocks-targets.
  • Is this a breaking change?
• Add a google_cloud_cpp_pubsub_mocks pkg

I have no idea if this works. Or how to test it.

But I can (from the demo-fedora-pr docker shell)

docker:demo-fedora$ ls /h/google-cloud-cpp-installed/lib64/cmake/google_cloud_cpp_pubsub_mocks/
google_cloud_cpp_pubsub_mocks-config-version.cmake  pubsub_mocks-targets.cmake
google_cloud_cpp_pubsub_mocks-config.cmake

# the pubsub one has a `noconfig.cmake`... whatever that means.

docker:demo-fedora$ PKG_CONFIG_PATH="/h/google-cloud-cpp-installed/lib64/pkgconfig:${PKG_CONFIG_PATH:-}"
docker:demo-fedora$ pkg-config --validate google_cloud_cpp_pubsub_mocks

of course, GTest is not installed on that image, so I don't know what is being validated. /shrug

---

This change is 

[google-cloud-cpp-bot]

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[codecov]

Codecov Report

Base: 93.96% // Head: 93.97% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (dcab21d) compared to base (29bf45f).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #10008   +/-   ##
=======================================
  Coverage   93.96%   93.97%           
=======================================
  Files        1513     1513           
  Lines      139964   139964           
=======================================
+ Hits       131524   131532    +8     
+ Misses       8440     8432    -8     

Impacted Files	Coverage Δ
google/cloud/storage/parallel_upload.cc	98.62% <0.00%> (+0.34%)	⬆️
...cloud/pubsub/internal/subscription_session_test.cc	98.82% <0.00%> (+0.83%)	⬆️
...bigtable/examples/bigtable_hello_instance_admin.cc	83.00% <0.00%> (+2.00%)	⬆️

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[coryan]

I am not sure this is breaking either:

• How would a customer use the mocks library before? Did it work? If the answer is "it could not work" then this is not breaking, you are fixing a broken thing.

To test this, we need a thing in the cmake-install build that uses it. We typically hijack the quickstarts for that purpose, but maybe you need something more ad-hoc.

Maybe you could extend ci/verify_current_targets to also check the mocks?

[coryan]

nit: copyright year

[dbolduc]

Fixed.

[coryan]

if this was something like:

find_dependency(@GOOGLE_CLOUD_CPP_WE_NEED_A_NAME@)

then this file could be a generic file shared by all the libraries.

Maybe for a future PR?

[dbolduc]

I have taken a mental note.

We would probably use a macro for just the service name (e.g. pubsub) because we include @LIBRARY@-targets.cmake below.

[coryan]

There is a bit of a mess with FindGTest (the built-in module in CMake) vs. the config file installed by googletest:

https://cmake.org/cmake/help/latest/module/FindGTest.html

Maybe we should install a file like this and include it instead?

https://github.com/googleapis/google-cloud-cpp/blob/main/cmake/FindGMockWithTargets.cmake

[dbolduc]

As you pointed out, there is incremental progress to be made by installing in cases where FindGTest works. We can figure out how to test the other case in our CI later.

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