Update protobuf requirement from 3.6.1 to 3.7.0

[dependabot-preview]

Updates the requirements on protobuf to permit the latest version.

Release notes

Sourced from protobuf's releases.

Protocol Buffers v3.7.0

C++

• Introduced new MOMI (maybe-outside-memory-interval) parser.
• Add an option to json_util to parse enum as case-insensitive. In the future, enum parsing in json_util will become case-sensitive.
• Added conformance test for enum aliases
• Added support for --cpp_out=speed:...
• Added use of C++ override keyword where appropriate
• Many other cleanups and fixes.

Java

• Fix illegal reflective access warning in JDK 9+
• Add BOM

Python

• Added Python 3.7 compatibility.
• Modified ParseFromString to return bytes parsed .
• Introduce Proto C API.
• FindFileContainingSymbol in descriptor pool is now able to find field and enum values.
• reflection.MakeClass() and reflection.ParseMessage() are deprecated.
• Added DescriptorPool.FindMethodByName() method in pure python (c extension alreay has it)
• Flipped proto3 to preserve unknown fields by default.
• Added support for memoryview in python3 proto message parsing.
• Added MergeFrom for repeated scalar fields in c extension (pure python already has it)
• Surrogates are now rejected at setters in python3.
• Added public unknown field API.
• RecursionLimit is also set to max if allow_oversize_protos is enabled.
• Disallow duplicate scalars in proto3 text_format parse.
• Fix some segment faults for c extension map field.

PHP

• Most issues for json encoding/decoding in the c extension have been fixed. There are still some edge cases not fixed. For more details, check conformance/failure_list_php_c.txt.
• Supports php 7.3
• Added helper methods to convert between enum values and names.
• Allow setting/getting wrapper message fields using primitive values.
• Various bug fixes.

Ruby

• Ruby 2.6 support.
• Drops support for ruby < 2.3.
• Most issues for json encoding/decoding in the c extension have been fixed. There are still some edge cases not fixed. For more details, check conformance/failure_list_ruby.txt.
• Json parsing can specify an option to ignore unknown fields: msg.decode_json(data, {ignore_unknown_fields: true}).
• Added support for proto2 syntax (partially).
• Various bug fixes.

C#

• More support for FieldMask include merge, intersect and more.
• Increasing the default recursion limit to 100.
• Support loading FileDescriptors dynamically.
• Provide access to comments from descriptors.
• Added Any.Is method.

... (truncated)

Commits

• 582743b Update version number to 3.7.0 (#5793)
• 6eeab29 Merge pull request #5787 from BSBandme/3.7.x-fix
• 6030209 fix mac python cpp building (#5786)
• 400845a fix macos build for High Sierra (#5780)
• 0aad533 Add a script to mirror php changes to protobuf-php (#5778)
• 5d8cd3b Date and time need to be before version (#5777)
• 580e189 Merge pull request #5766 from TeBoring/3.7.x-fix
• b52754b Update version to 3.7.0rc3
• 05f5712 Support rc version in update_version.py (#5750)
• c7b3392 Update version to 3.7.0 (#5749)
• Additional commits viewable in compare view

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[dependabot-preview]

Superseded by #294.