Update migration docs

[Veki301]

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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
  • contains a reference JIRA issue number like SQPIT-764
  • 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

Briefly describe the issue you have solved or implemented with this pull request. If the PR contains multiple issues, use a bullet list.

Causes (Optional)

Briefly describe the causes behind the issues. This could be helpful to understand the adopted solutions behind some nasty bugs or complex issues.

Solutions

Briefly describe the solutions you have implemented for the issues explained above.

Dependencies (Optional)

If there are some other pull requests related to this one (e.g. new releases of frameworks), specify them here.

Needs releases with:

• GitHub link to other pull request

Testing

Test Coverage (Optional)

• I have added automated test to this contribution

How to Test

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Notes (Optional)

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Attachments (Optional)

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PR Post Submission Checklist for internal contributors (Optional)

• Wire's Github Workflow has automatically linked the PR to a JIRA issue

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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.

[CLAassistant]

All committers have signed the CLA.

[arthurwolf]

Looks great.