Safe Mode capability

[stiiifff]

Having the ability to temporarily pause transfers & normal operations on a live parachain is a valuable mechanism, when an issue / attack occurs. This is especially useful during the launch period of a parachain whereby the runtime code might not always have been battle-tested yet. Past this initial period, the chain’s Governance body (or Sudo account(s)) could decide to remove this capability to fully decentralize the network. The Substrate FRAME library contains the SafeMode & TxPause pallets which allow to implement such a mechanism.

• Integrate the FRAME SafeMode & TxPause pallets with sane defaults in both devnet & mainnet runtimes (disabled by default in both runtimes).
• SafeMode should only allow balance transfers as whitelisted call. Permissionless operations (enter, extend) should be disabled. Only a privileged origin can enable / disable safe mode: ForceEnterOrigin, ForceExtendOrigin & ForceExitOrigin to be configured as the Root origin (Sudo).
• TxPause PauseOrigin & UnpauseOrigin to be configured as the Root origin (Sudo).

Depends on #71

[Daanvdplas]

I would like to take this one :)

Edit: will need to wait for v1.1.0

[Moliholy]

@Daanvdplas Do you still want to pick up this issue? I just completed the equivalent issue for Trappist, so I thought to complete it here.

[Daanvdplas]

Go for it!