feat: add UnknownStrategy enum for future-proofing

[vitorhugods]

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PR Submission Checklist for internal contributors

• The PR Title

  • conforms to the style of semantic commits messages¹ supported in Wire's Github Workflow²
  • answers the question: If merged, this PR will: ... ³

• The PR Description

  • is free of optional paragraphs and you have filled the relevant parts to the best of your ability

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What's new in this PR?

Issues

When introducing some message types, clients that are not ready to receive them yet might react in improper ways.

iOS warns about all received unknown messages while Android and Web ignore unknown message types.

This isn't currently unified between clients and there's no way of choosing a different approach depending on the newly introduced message type.

Solutions

As proposed in the internal RFC, add a new field called unknownStrategy to be sent beside the actual message content. If content is NULL/NONE, the unknownStrategy can give a hint of what to do and how to handle such message.

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PR Post Merge Checklist for internal contributors

• If any soft of configuration variable was introduced by this PR, it has been added to the relevant documents and the CI jobs have been updated.

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References

1. https://sparkbox.com/foundry/semantic_commit_messages
2. https://github.com/wireapp/.github#usage
3. E.g. feat(conversation-list): Sort conversations by most emojis in the title #SQPIT-764.

[MohamadJaara]

LGTM

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud