[Important proposal] Decentralized or Federated snap store operation structure similar ubuntu mirrors

Updated according to comments:

**Where it applies?**
Snap CLI

**Where it does not apply**
- Snapcraft Website / Developer account
- Snap Desktop Client / Gnome software
(Desktop client is a GUI for display software lists, select to download / uninstall them and this is not important for most linux users or all power users but downloads should work using configured mirror)

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About Snap CLI
CLI is our traditional method for install softwares.

e.g. sudo apt install gimp
snap then, sudo snap install gimp

You can add support for global mirrors and suggest for interested parties to register

https://launchpad.net/ubuntu/+archivemirrors
For example: India mirror
- APT mirror - mirror.hosted-domain.in
- Snap mirror - snap-mirror.hosted-domain.in

Benefits:
* Reduce server maintain costs (+snapstore day by day become popular)
* Most fastest downloads when connect to regional servers
* Users don't need connect to overseas servers or centralized environment and privacy friendly
* About organizations, enterprises use-cases - I believe this will be good solution for them to keep head out from overseas networks and let everyone to get apps from snap.
(and for companies that don't connect their systems to public internet)

Private stores/ Brand store - You can get benefit from this feature request to fulfill many expected desires

(Related request about mirror option: https://bugs.launchpad.net/snapstore-server/+bug/1767118, not only for that country; other countries also experience same issue. basically mirror apt downloads more faster than to snap store)

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[Un-related] **What happen to metrics?**
You can get them as how it works currently. It's not related to this.
(Or if you like you can find someway to implement it to work with mirrors custom sub-domain to sync under specific interval to main server.

[Un-related] **Can we implement this to desktop client?**
I don't know. again, it's upto you. You'll have to improve to load images etc using mirror servers domains.

images and static contents - snapcdn-mirror.region.org

[Un-related] (Additional desktop client facilities)
Sign-in - As i know it use for get access to private and unlisted apps., it need connect to canonical servers directly for provide access to account and then able to match(retrieve) ID of particular app then client know where has it on mirror server to download
 or if you decide, private/unlisted apps are confidential then avoid sync those apps to mirror servers and let to download from main servers as now.
(Basically sign-in option in client only use by small amount of users for certain purposes when compare with total snap store users)