introduce `accounts.email.order` for aerc accounts

[RyanGibb]

Description

Nix does not preserve attrset order, instead sorting attributes by alphabetical order https://github.com/NixOS/nixpkgs/issues/81986.

However, aerc displays accounts based on their order in .config/aerc/accounts.conf.

This PR introduces a accounts.email.order list that provides an optional order for accounts in accounts.email.accounts.

I implement support for this in the aerc module, and I suspect other front-ends might also be able to benefit from this.

If a partial order is provided those will be ordered after the primary account, and any unordered accounts will be included with the previous alphabetical behavior after.

Checklist

• [x] Change is backwards compatible.

  • The primary account is still displayed first and if no order list is provided the previous behavior is maintained.

• [x] Code formatted with ./format.

• [x] Code tested through nix-shell --pure tests -A run.all or nix develop --ignore-environment .#all using Flakes.

• [ ] Test cases updated/added. See example.

• [x] Commit messages are formatted like

  {component}: {description}
  
  {long description}
  

  See CONTRIBUTING for more information and recent commit messages for examples.

Maintainer CC

@lukasngl

[RyanGibb]

Hi @olmokramer, just putting a gentle ping here.

[olmokramer]

Oh I'm sorry for just disappearing into the void! I think the changes look good! But I'm not in a position to merge PRs, sorry, I should have been more clear about that.

[RyanGibb]

No problem at all! Thanks for the approval :-)

[RyanGibb]

Can I ask what you think of this @rycee ?

[stale[bot]]

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[RyanGibb]

Rebased on master

[stale[bot]]

Thank you for your contribution! I marked this pull request as stale due to inactivity. Please read the relevant sections below before commenting.

If you are the original author of the PR

• GitHub sometimes doesn't notify people who commented / reviewed a PR previously when you (force) push commits. If you have addressed the reviews you can officially ask for a review from those who commented to you or anyone else.
• If it is unfinished but you plan to finish it, please mark it as a draft.
• If you don't expect to work on it any time soon, please consider closing it with a short comment encouraging someone else to pick up your work.
• To get things rolling again, rebase the PR against the target branch and address valid comments.

If you are not the original author of the PR

• If you want to pick up the work on this PR, please create a new PR and indicate that it supercedes and closes this PR.

[RyanGibb]

This is finished, but I'm no longer interested in trying to get it merged.