Added flow for discovery

Why is this change being made?

Following a couple of conversations, I'd like to come up with a shared understanding on how an issue becomes ready for development. The problems the MR would like to solve:

• there was much complaint from engineers about being lost among the many issues we open during discovery. When do we open a new issue?
• Maria lacked engineering feedback on design issues. When and why are engineers invited to provide feedback?
• I thought on emphasizing the role of discovery, beside delivery. What is the role of discovery?

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per [say-why-not-just-what][transparency]
• Assign this change to the correct DRI
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