feat(python): support for pypi parse syntax and string concatenation

[neskk]

🤔 What's changed?

Support the pypi-parse step definition matcher used by behave and pytest-bdd - both python frameworks.

• Added support for string concatenation both for plain and pypi-parse syntaxes.
• Added tree-sitter query to match pypi parse syntax:
  • @step(parsers.parse("step-def"))
  • @step(parse("step-def"))
  • @step(parse("step-" + "d" + "ef"))
  • @step(parse("step-def {date:valid_date}", custom_types))

⚡️ What's your motivation?

I'm currently using pytest-bdd for running cucumber tests, but because I'm using PyPi Parse for step-definitions, the cucumber-plugin won't recognize them.

Supersedes #206.
Closes #205.

🏷️ What kind of change is this?

• ⚡ New feature (non-breaking change which adds new behaviour)

♻️ Anything particular you want feedback on?

I haven't been able to run the cucumber vscode extension, so I couldn't test it "in action".

I have modified the unit-test step-definitions to include at least one test for each different syntax.

📋 Checklist:

• I agree to respect and uphold the Cucumber Community Code of Conduct
• I've changed the behaviour of the code
  • I have added/updated tests to cover my changes.
• My change requires a change to the documentation.
  • I have updated the documentation accordingly.
• Users should know about my change
  • I have added an entry to the "Unreleased" section of the CHANGELOG, linking to this pull request.

[neskk]

@kieran-ryan The step-def syntax works but now the parameter type queries identify named parameters, e.g.: @when(parse("make a request to {url}")) as a parameter type.

[neskk]

@kieran-ryan any ideas on how can we differentiate expressions coming from "parse" definitions from standard cucumber expressions?

# cucumber
@step("a cucumber expressions {custom_param_type}")
# pytest-bdd
@step(parsers.parse("a pypi {param_name_not_a_type}"))
@step(parsers.parse("a pypi {param_name:param_type}"))

I don't know how we can support the named parameters in step-defs that use the pypi parse, at the same time we support custom param types.
These two approaches effectively use the same syntax with different meaning:

• in pypi parse {xxx} is a named parameter
• in cucumber expressions {xxx} is a parameter type
  Because of this, the step-defs with "parse" syntax are discovered and indexed, but they throw errors for not defining the parameter types.

[neskk]

I realized that Pytest-BDD 8.0.0+ adds support to the official gherkin-parser.
Update: I thought this new pytest-bdd version would support cucumber-expressions, but it still doesn't.

This MR still has a problem with Parameter Types. Even though the step-defs are picked up by the language-service, it fails to parse parameters on step-definitions. E.g.:

@when(parse("bla bla bla {arg1}"))
def bla_bla_bla(arg1: str):
  // do something with arg1

This fails with something like: ParameterType "arg1" not found.