feat: support auto converting doc strings to plain strings

[chirino]

This PR allows you to implement the following step:

  Scenario: example
    Given call with:
    """
    text
    """

with a simpler function signature like:

ctx.Step(`^call with:$`, func(arg string) error {
	return nil
})

vs. what you have to do now which is:

ctx.Step(`^call with:$`, func(arg *godog.DocString) error {
	return nil
})

[codecov]

Codecov Report

Merging #380 (80eb14d) into master (3589a9b) will increase coverage by 0.09%.
The diff coverage is 62.50%.

@@            Coverage Diff             @@
##           master     #380      +/-   ##
==========================================
+ Coverage   81.03%   81.13%   +0.09%     
==========================================
  Files          25       25              
  Lines        1993     1998       +5     
==========================================
+ Hits         1615     1621       +6     
+ Misses        275      274       -1     
  Partials      103      103              

Impacted Files	Coverage Δ
internal/models/stepdef.go	61.06% <62.50%> (+2.72%)	⬆️

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[lonnblad]

Hi @chirino, thanks for the contribution!

Could you add a test in this file as well.
https://github.com/cucumber/godog/blob/master/internal/models/stepdef_test.go

Thanks!
BR Fredrik

[chirino]

ok test added.

[aslakhellesoy]

Hi @chirino,

Thanks for your making your first contribution to Cucumber, and welcome to the Cucumber committers team! You can now push directly to this repo and all other repos under the cucumber organization! 🍾

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