Integrating LockBox to DBTransaction - introducing lockMulti

[CMCDragonkai]

Description

As well as defaulting some types, this should simplify it usage inside js-db where we are using LockBox to enable PCC locking for the transactions.

Issues Fixed

• Relates to Introduce Snapshot Isolation OCC to DBTransaction js-db#19

Tasks

• 1. Add Lockable as a default type for all the generic types depending on it
• [ ] 2. Extend the LockRequest type so that string can be taken, and if so, it is assumed that this is just a Lock normally - done on user side
• 3. Make lock releasers idempotent
• 4. Enable the ability to do lock mapping for LockBox, where we return a collection of ResourceAcquire<L> instead of a single resource acquisition, this is useful for DBTransaction as it has to manage locking imperatively
• 5. Changed the LockRequest type to MultiLockRequest, this breaks some type signatures, so this is a major upgrade

Final checklist

• Domain specific tests
• Full tests
• Updated inline-comment documentation
• Lint fixed
• Squash and rebased
• Sanity check the final build

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Legend

[CMCDragonkai]

I have to remove LockBox.unlock because it doesn't make sense for LockBox when used with RWLockReader and RWLockWriter. The DBTransaction has to replicate some of the functionality of LockBox.

See: MatrixAI/js-db#19 (comment)

The core problem is that the Lockable interface prevents us from allowing lock to return a "collection" of releases. Instead only 1 release function can be returned, and that is the composite of the smaller releases. There is no way to decompose ResourceRelease into smaller ResourceRelease.

Alternatively, LockBox exposes a different function that gives back all the release information, the users still have to keep track of lockReleasers: Map<string, ResourceRelease>, but they could use the alternative function which does the same as LockBox.lock but is given more useful information at the end. Rather than a single ResourceAcquire, it returns a collection of ResourceAcquire. It would also need to present the key information as it has been re-ordered.

Something like this:

  public lockMany(...requests: Array<LockRequest<L>>): Array<[ToString, ResourceAcquire<L>]> {
    return [];
  }

[CMCDragonkai]

This will update to 3.0.0.