Database

[andrevmatos]

Fixes #2044
Fixes #1933
Fixes #1831
Fixes #2025
Fixes #2056
Fixes #2077
Fixes #2085
Fixes #1618
Fixes #1615

Short description
Use PouchDB (backed by default by IndexedDB on browsers, LevelDown on NodeJS) as a persistent storage to store state.
Only pending transfers are kept in Redux (in memory) state, and synced to the database as soon as they change, by a persister middleware. This gives us the speed of in-memory access, the backends/adapters/sync power of Pouch, and memory-safety of not keeping everything in memory all the time and instead accessing historic data only if needed.
RaidenState/Channels is kept in memory (Redux) and just synced asynchronously to the db (per individual top level keys, and individual channels).
Transfers state, as they can grow boundless (#1618), is kept on database and retrieved on demand if needed using secondary indexes. This allows us to keep sub-0.2s transfers (cli-to-cli, nodejs, webrtc) while saving everything at real time to avoid losing state.
Legacy (once) and new async migration schemas are also implemented.

Definition of Done

• Steps to manually test the change have been documented
• Acceptance criteria are met
• Change has been manually tested by the reviewer (dApp)

Steps to manually test the change (dApp)

[github-actions]

You modified raiden-dapp/src,
Please remember to add a change log entry at raiden-dapp/CHANGELOG.md if necessary.

[codecov]

Codecov Report

Merging #2110 into master will increase coverage by 6.98%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2110      +/-   ##
==========================================
+ Coverage   87.69%   94.68%   +6.98%     
==========================================
  Files         159      154       -5     
  Lines        5999     6093      +94     
  Branches     1137     1064      -73     
==========================================
+ Hits         5261     5769     +508     
+ Misses        676      261     -415     
- Partials       62       63       +1     

Flag	Coverage Δ
#dapp	91.73% <ø> (ø)
#sdk	95.89% <ø> (+9.89%)	⬆️
#sdk_e2e	67.85% <ø> (?)
#sdk_unit	85.14% <ø> (-0.86%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
raiden-dapp/src/services/raiden-service.ts	87.50% <ø> (ø)
raiden-ts/src/channels/epics.ts	97.36% <ø> (+0.55%)	⬆️
raiden-ts/src/channels/reducer.ts	98.11% <ø> (+1.11%)	⬆️
raiden-ts/src/channels/state.ts	100.00% <ø> (ø)
raiden-ts/src/channels/utils.ts	96.80% <ø> (+0.03%)	⬆️
raiden-ts/src/config.ts	100.00% <ø> (ø)
raiden-ts/src/db/epics.ts	100.00% <ø> (ø)
raiden-ts/src/db/migrations.ts	100.00% <ø> (ø)
raiden-ts/src/db/utils.ts	94.25% <ø> (ø)
raiden-ts/src/epics.ts	96.61% <ø> (+0.11%)	⬆️
... and 55 more

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[andrevmatos]

This is too big to get reviewed. I'll merge as is, and we can test and narrow down any issues on our development branch (master) ;)