* chore(python): drop python 3.6

Source-Link: googleapis/synthtool@4f89b13
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:e7bb19d47c13839fe8c147e50e02e8b6cf5da8edd1af8b82208cd6f66cc2829c

* require python 3.7+ in setup.py

* remove python 3.6 sample configs

* exclude templated README

* remove python 3.6 from noxfile

* remove python 3.6 from remaining files

* remove testing/constraints-3.6.txt

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
Co-authored-by: Anthonios Partheniou <[email protected]>

* chore(deps): update actions/setup-python action to v4

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

Co-authored-by: Anthonios Partheniou <[email protected]>
Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

ADC login command for gcloud is `gcloud auth application-default auth login`

Co-authored-by: Anthonios Partheniou <[email protected]>

…[autoapprove] (#424)

Source-Link: googleapis/synthtool@1f37ce7
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:8e84e0e0d71a0d681668461bba02c9e1394c785f31a10ae3470660235b673086

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Source-Link: googleapis/synthtool@69fabae
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:562802bfac02e012a6ac34eda282f81d06e77326b82a32d7bbb1369ff552b387

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Source-Link: googleapis/synthtool@c4dd595
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:ce3c1686bc81145c81dd269bd12c4025c6b275b22d14641358827334fddb1d72

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

…cts (#428)

* feat: Make grpc transcode logic work in terms of protobuf python objects

(for context: [gRPC Transcoding](https://github.com/googleapis/googleapis/blob/master/google/api/http.proto#L44))
Previously it worked on dictionaries only, but that causes problems.

In GAPIC the dictionaries are created through the same logic as JSON (there is no better built-in way), thus applying [protobuf json mapping](https://developers.google.com/protocol-buffers/docs/proto3#json) conversion logic in the process. Unfortunately converting a protobuf object to a dictionary and to JSON, although similar, are not the same thing. Specifically the `Timestamp`, `Duration`, `FieldMask`, `uint64`, `int64`, and `*Value` protobuf messages are converted to strings for JSON (instead of being properly converted to dicts for most of those types, and `int64/uint64` converted to `int` respectively). As a result a rountrip that GAPIC was relying on (protobuf object -> dict -> transcode -> protobuf object) did not work properly. For example, when converted to dictionary, every int64 field would be converted to `string` (because it is what proto-JSON mapping spec requires), but later, when we need to rebuild a message from a transcoded dictionary that would fail with the following error:
```
TypeError: '0' has type str, but expected one of: int
```

Note, `*Rules` thing from proto-plus does not help, becuase the type may happen inside common native protobuf stub messsages (like `google.type.Money`), fields of which are outside of scope of the proto-plus custom conversion logic.

Also, this change greatly simplifies the procedure of transcodding, eliminating multiple conversion steps (to and from dictionaries multiple times) making the whole logic significanly more efficient (python gapics are nutoriously known to be slow due to proto-plus stuff, so efficiency is important) and robust (JSON conversion logic does not interfere anymore with pure protobuf objects grpc transcoding)

* reformat code using black

* reformat code according to flake8

Co-authored-by: Anthonios Partheniou <[email protected]>

…430)

Source-Link: googleapis/synthtool@fdba3ed
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:1f0dbd02745fb7cf255563dab5968345989308544e52b7f460deadd5e78e63b0

docs: add a note that grpcio-gcp is only supported in environments with protobuf < 4.x.x
docs: raise DeprecationWarning when 'grpcio-gcp' is used
fix(deps): require protobuf >= 3.20.1

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>