ScenarioTagTrait is not intuitive to use

[pfrenssen]

I have a step definition that depends on the @email tag being present and I tried retrieving this using the ScenarioTagTrait. It appears this trait will only retrieve the tags for both the scenario and the feature inside a @beforeStep hook, it won't work in any other hooks or step definitions. ::getCurrentScenarioTags() expects a StepScope to be passed, this is only available in @beforeStep hooks. It looks this is the case because this has been written specifically for MinkContext::beforeJavascriptStep(). It seems it should be possible to make this more universally usable by making a few modifications.

• It would be handy to always return the tags for the scenarios as well as the features. To make it clear this works not only for scenario tags I would rename this from ScenarioTagTrait to just TagTrait.
• In addition to ::registerScenario() we can implement a ::registerFeature() method that keeps track of the current feature, and a ::getFeature() method to return it.
• ::getCurrentScenarioTags() could be renamed to ::getTags() and doesn't need a StepScope passed into it any more. It can instead call ::getFeature().
• Since most of the time the developer would be interested whether a particular tag is present, it would be a nice addition to add a ::hasTag(string $tag): bool method.