Optional params and internal invokable calls

Proposed changes

Call a invokable function was not possible due to the params manipulation of the decorator. This PR fixes the problem for internal function invocation by keeping track of the parameters in the right position. Also, while performing these changes, the lack of an OptionalParam decorator was evident, thus it was included to cover those scenarios.

Types of changes

What types of changes does your code introduce to Convector?

[x] Bugfix (non-breaking change which fixes an issue)
[x] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

[x] I have read the CONTRIBUTING doc
[x] Lint and unit tests pass locally with my changes
[ ] All the commits have been squashed into a single commit following the conventional commits guide
[x] All the commits are signed with git sign-off
[x] I have added tests that prove my fix is effective or that my feature works
[ ] I have added necessary documentation (if appropriate)

Further comments

When you have an optional param in your invokable method, simply decorate it with @OptionalParam() in order to convector be aware of it and process it accordingly.

  @Invokable()
  public async optionalParam(
    @Param(yup.string())
    name: string,
    @OptionalParam()
    @Param(yup.string())
    sufix: string = 'test'
  )

hyperledger-labs / convector