represent numbers from JSON as rust_decimal::Decimals

[zancas]

This change makes all values that are read from JSON, and are numbers to be "Decimals".

Decimals have explicit-and-fixed precision. Numbers written down in JSON, also have explicit and fixed precision.

Because of this, the correct representation for JSON numbers is a Decimal.

The change is:

• add a dependency on the rust_decimal crate to the manifest (Cargo.toml) file
• add a use statement to shorten the name of rust_decimal::Decimal, a type we are choosing to use
• replace i64, u64, and f64 type annotations in the types-generated-from JSON with Decimal

[dannasessha]

Is there another way to achieve the function of the use statement?

If so, what are the pros and cons of using a use?

[dannasessha]

The approach seems well-reasoned and the changes look fine.

Running cargo test --all yields 3 passed tests.

test getinfo ... ok test getblockchaininfo ... ok test z_getnewaddress ... ok

[AloeareV]

Is there another way to achieve the function of the use statement?

If so, what are the pros and cons of using a use?

In most situations, use foo::Blar can be removed by explicitly pathing, i.e. replacing any calls to Blar with foo::Blar. However, in order to call a trait method, you need to bring the trait into scope by 'use'ing it. We like to do this by saying use Bandana as _ to make it clear the thing we are useing is being brought into scope, and not directly accessed.