Expose key Build Boost economic data via subscription

[Tartuffo]

This data can be used in Blockchain Explorers and via sites like The Graph for the community to get key information about the state of the RUN Protocol components.

From our meeting on Feb 22, here is the data we want to expose from getRUN:

1. Per Contract (assetNotifier)
   1. Net amount minted (totalDebt)
   2. Total collateral
   3. Governance parameters (see Expose RUN protocol governance state via subscription #5268)
      1. debt limit
      2. allowed ratio
      3. interest rate
2. Per Account
   1. Locked BLD amount (locked)
   2. Debt (debtSnapshot)
   3. Interest rate (?) interestRate (but see Refactor vault notifications to not cascade interest charge events #4540)

• publicFacet method to get assetNotifier

[dckc]

The current code (52f60eb) has an assetNotifier on each offer result:

const assetNotifer: Notifier<{
    compoundedInterest: Ratio;
    interestRate: Ratio;
    latestInterestUpdate: bigint;
    totalDebt: Amount<"nat">;
}>

There's no publicFacet method to get that assetNotifier; the only way to get it is as a result of opening an account. That seems like a bug.

The Per Account notifier is updated as follows:

    /** @type {VaultUIState} */
    const result = harden({
      // TODO move manager state to a separate notifer https://github.com/Agoric/agoric-sdk/issues/4540
      interestRate: manager.getInterestRate(),
      liquidationRatio: manager.getMintingRatio(),
      debtSnapshot: { debt, interest },
      locked: getCollateralAmount(),
      // newPhase param is so that makeTransferInvitation can finish without setting the vault's phase
      // TODO refactor https://github.com/Agoric/agoric-sdk/issues/4415
      vaultState: newActive ? 'active' : 'closed',
    });

The VaultUIState type is not declared, so it defaults to any. :-/ (more interest on technical debt: #3916 )

[dckc]

@Tartuffo @rowgraus what is an "interest rate curve"?

[dckc]

And what does "Distribution of utilization of loan amount" mean, @rowgraus ? @Tartuffo ?

[dckc]

It's not clear how useful Total collateral is; @btulloh asks for "a detailed view into the state changes, rather than summary data".