Demo sender fallback

[arminsabouri]

Code migrated from #1164. There were many conflicts.

The tricky thing with v2 is we don't want to fallback when there is a transient error. Luckly, our session outcome abstracts all that away. If after a replay a session is closed due to either a failure or cancellation we broadcast the fallback. But this requires a replay. Say your payjoin proposal was faulty, currently you have to resume again for the fallback to be broadasted which I think defeats the purpose of a "demo". i.e what we wants devs to replicate in their apps.

Instead, internally in Pj-cli we can replay again if an error occured (or if #1197 we can avoid disk reads) check if the session is closed and fallback accordingly.

cc @zealsham @chavic

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[coveralls]

Coverage Report for CI Build 25166916130

Coverage increased (+0.2%) to 85.159%

Details

• Coverage increased (+0.2%) from the base build.
• Patch coverage: 2 uncovered changes across 1 file (100 of 102 lines covered, 98.04%).
• 1 coverage regression across 1 file.

Uncovered Changes

File	Changed	Covered	%
payjoin-cli/src/app/v2/mod.rs	102	100	98.04%

Coverage Regressions

1 previously-covered line in 1 file lost coverage.

File	Lines Losing Coverage	Coverage
payjoin-cli/src/app/v1.rs	1	69.62%

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Coverage Stats

Relevant Lines:	13530
Covered Lines:	11522
Line Coverage:	85.16%
Coverage Strength:	397.15 hits per line

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💛 - Coveralls

[DanGould]

What's left to do here? Just a v2 fallback test? Or we're still not handling the v2 case completely and a decision needs to be made on the experience?

[arminsabouri]

What's left to do here? Just a v2 fallback test? Or we're still not handling the v2 case completely and a decision needs to be made on the experience?

I decided a second resume was not the way forward. PJ cli will replay and check for the fallback condition before exiting the app. Fall back test was added as a integration test in pj cli as opposed to a e2e test. Creating e2e conditions for protocol failure was tricky without manually updating the db. Integration test ended up being simpler .