Add timestamp to Attachment

[davidjgoss]

🤔 What's changed?

Add Attachment.timestamp

⚡️ What's your motivation?

Part of cucumber/common#2271.

During test and step executions the execution might produce multiple attachments. For longer steps the exact timing of when the attachments were captured might be important. Currently the Attachment envelop[e] type does not have a timestamp and therefore this information cannot be captured and used.

It makes sense to do this now because we already have the signature change for Attachment in #301 which isn't released yet.

🏷️ What kind of change is this?

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

📋 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.

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[ehuelsmann]

Looks good to me.

[luke-hill]

Question (More from the other PR), should we add to the changelog that the prior attribute is now deprecated and will be removed in the next 1/2/3 majors time?

[mpkorstanje]

LGTM, but this is a breaking change.

[davidjgoss]

Question (More from the other PR), should we add to the changelog that the prior attribute is now deprecated and will be removed in the next 1/2/3 majors time?

Good point, will do that in a separate commit before releasing.

[davidjgoss]

LGTM, but this is a breaking change.

Agreed, will release as a major.