[WIP] Runtime Migration Tutorial

[apopiak]

First draft for a runtime migration tutorial.

This is kind of blocked by the availability of paritytech/substrate#7208 and paritytech/substrate#7451 in a released Substrate version as I would like to use the pallet version as a storage guard.

aims to resolve #766

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• Are the audience and objective of the document clear? E.g. a document for developers that should teach them about transaction fees.
• Is the writing:
  • Clear: No jargon.
  • Precise: No ambiguous meanings.
  • Concise: Free of superfluous detail.
• Does it follow our style guide?
• If this is a new page, does the PR include the appropriate infrastructure, e.g. adding the page to a sidebar?
• Build the page ($ cd website && yarn start). Does it render properly? E.g. no funny lists or formatting.
• Do links go to rustdocs or devhub articles rather than code?
• If this PR addresses an issue in the queue, have you referenced it in the description?

[apopiak]

working on code here:
https://github.com/substrate-developer-hub/substrate-node-template/tree/apopiak-migration-tutorial

[apopiak]

Dan working on code here: https://github.com/danforbes/substrate-node-template/tree/df/tut/adv-upgrade

[JoshOrndorff]

FYI, this is (a cleaned up version of) the runtime migration code I presented in seminar.

code: https://github.com/JoshOrndorff/recipes/tree/joshy-migration-station
seminar recording: https://www.youtube.com/watch?v=0eNGZpNkJk4&list=PLp0_ueXY_enXRfoaW7sTudeQH10yDvFOS

[nuke-web3]

Is it safe to say apopiak/migration-example#2 when completed will lay foundations for this to be closed? @apopiak Let us know how / if we can help in any way to get this tuto in the devhub 🥳

[apopiak]

Current plan (as I understand it) is to have a combination of knowledge base, recipes and the repo you mention and not have a migration tutorial. @sacha-l Feel free to weigh in with plans :-)