fix: add decimal lib in dependencies

[davidjulien]

Hello!

Currently, decimal is added indirectly because ecto is an (optional) dependency in mix.exs.

However, if the project where you want to add logger_json doesn't have ecto in its dependencies, decimal is not added and then logger_json doesn't compile:

==> logger_json
Compiling 17 files (.ex)
    error: Decimal.__struct__/0 is undefined, cannot expand struct Decimal. Make sure the struct name is correct. If the struct name exists and is correct but it still cannot be found, you likely have cyclic module usage in your code
    │
 39 │   def encode(%Decimal{} = decimal, _redactors), do: decimal
    │              ^
    │
    └─ lib/logger_json/formatter/redactor_encoder.ex:39:14: LoggerJSON.Formatter.RedactorEncoder.encode/2

== Compilation error in file lib/logger_json/formatter/redactor_encoder.ex ==
** (CompileError) lib/logger_json/formatter/redactor_encoder.ex: cannot compile module LoggerJSON.Formatter.RedactorEncoder (errors have been logged)
    lib/logger_json/formatter/redactor_encoder.ex:39: (module)
could not compile dependency :logger_json, "mix compile" failed. Errors may have been logged above. You can recompile this dependency with "mix deps.compile logger_json --force", update it with "mix deps.update logger_json" or clean it with "mix deps.clean logger_json"

You can easily reproduce the bug by removing the ecto dependency in the logger_json mix.exs file. You will see that the decimal dependency disappears in deps.tree and that the lib doesn't compile anymore (same error as above).

➜  mix deps.get
Resolving Hex dependencies...
Resolution completed in 0.055s
New:
  castore 1.0.8
  dialyxir 1.4.3
  earmark_parser 1.4.41
  erlex 0.2.7
  ex_doc 0.34.2
  excoveralls 0.18.3
  jason 1.4.4
  junit_formatter 3.4.0
  makeup 1.1.2
  makeup_elixir 0.16.2
  makeup_erlang 1.0.1
  mime 2.0.6
  nimble_parsec 1.4.0
  plug 1.16.1
  plug_crypto 2.1.0
  stream_data 1.1.1
  telemetry 1.3.0
All dependencies are up to date

It may be interesting to refactor the code in another PR so that decimal encoding is not compiled when decimal dependency doesn't exist in the project.

Regards

[coveralls]

coverage: 100.0%. remained the same
when pulling d7ebd67 on davidjulien:fix-missing-decimal-dependency
into 1371032 on Nebo15:master.

[tompesman]

I think it should be an optional dependency. Not every project has the decimal dependency included.

[davidjulien]

I opened another PR where we checked if the Decimal module is compiled to decide if the compiler includes the clause related to it. It was easier than I thought initialy.

[AndrewDryga]

Merged a PR that checks if Decimal is present, thank you ❤️

[tompesman]

Awesome! 🚀