Allow parachain to renew lease without actually run another parachain

[xlc]

One way to renew lease of a parachain is by perform lease swap with another parachain with an active lease. Many parachain teams are using this strategy to bid parachain slots before lease ends to secure future leases.

However, to in order to swap lease, it requires a XCM from both parachain to call swap. This means parachain team will have to build, run, and operate one more parachain just to renew the lease.

IMO this is unnecessary work for everyone. The parachain owner should be able to call swap without actually run the parachain.

[Tomen]

related to paritytech/polkadot#6592

[Tomen]

As far as I understand, this issue only applies to crowd loans as a means to extend slots. The main issue for this is #877

Self-bidding on auctions is possible without the mentioned problem.

[xlc]

We have self-bidding para and have exactly this issue.

[SBalaguer]

There are two things clashing here:

• If you opened a crowdloan to win a slot and you wish to open a new crowdloan with the same paraID to extend your lease without the original slot ending (which will always be the case, as the crowdloan dissolves once your slot ends), then you can't do it. This is what happened to Mangata.
• If you win a slot (self-bid or crowdloan) that has overlapping LPs with your current slot, you will need to register a new parachain and swap. This is currently Karura's issue. A possible solution for this is instead of bidding for all LPs on an auction, bid for those that are not overlapping yours with your current paraID. This could only be achieved with self-bidding, as if not it will be the same issue as explained on the previous point.

[kianenigma]

related: #877

[xlc]

closed by #1290