Quote maybe atoms

[sile]

Proposed Changes

Basically, ra codebase quotes maybe atoms (to support the maybe feature in the future I guess).
However there are some maybe atoms that are not quoted, and ra can't be compiled if the maybe feature is enabled.
This PR fixes this problem.
Of course, this is not a critical problem. So, feel free to close this PR if it seems not needed.

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[michaelklishin]

maybe in this case is a type name. It's a bit unexpected that the same quoting rules would apply to type specs since there cannot be any conflict with the maybe keyword.

Also, Ra is compiled and passes all tests on CI on Erlang 26 (where maybe is supposedly always enabled). But Make-based tests fail with this PR.

What am I missing?

[michaelklishin]

Maybe (pun intended) we should sidestep the issue entirely :) #402

[sile]

Thank you for your comments.

Seeing the OTP 26 highlight, the runtime's maybe feature is enabled by default, but the compiler's is not.
If we enable the compiler's maybe feature, ra cannot be compiled as follows:

// Erlang/OTP version
$ erl -boot start_clean -noshell -eval 'io:format(erlang:system_info(system_version)).' -s init stop
Erlang/OTP 26 [erts-14.1] [source] [64-bit] [smp:10:10] [ds:10:10:10] [async-threads:1] [jit]

// Clone ra
$ git clone https://github.com/rabbitmq/ra.git 
$ cd ra/

// Compile ra_log.erl without and with the maybe_expr compile feature 

// without (default) => OK
$ erlc src/ra_log.erl

// with => NG
$ erlc -enable-feature maybe_expr src/ra_log.erl
src/ra_log.erl:549:6: syntax error before: 'maybe'
%  549|     {maybe(log_entry()), state()}.
%     |      ^

[sile]

Maybe (pun intended) we should sidestep the issue entirely :) #402

The approach of #402 is perfect for me :)
Thank you!