Adapter calculate and retrieve total spendable amount

[simzzz]

Implemented adapter.get_deposit(...)for the Ethereum and Dummy adapters, including an integration test.

Change Log:

• adapter::EthereumAdapter - Added a get_deposit() function which calculates and returns total spendable amount, using the OUTPACE and ERC20 ABI's.
• adapter::ethereum::Error - Added two new possible errors. The first being TokenNotWhitelisted which is returned when the function is called with a channel with a deposit asset not being in the config's whitelist. The second is InvalidDepositAsset which is used when a channel's deposit asset cannot be converted to Address. This error is here temporarily and I assume it will be gone soon when the channel_v5 replaces the old channel in the adapter.
• dev.toml and prod.toml configs - Changed the structure of token_addr_whitelist from an array of strings, to an array with objects that contain address, min_token_units_for_deposit and precision.
• primitives::adapter::Deposit - new struct representing the get_deposit() output. Added signature for get_deposit in the impl
• primitives::channel_validator::asset_listed() - Changed asset_listed() function to work with the new token whitelist structure from String Vec to HashMap.
• primitives::config - Changed token whitelist from String Vec to HashMap. Added a new struct called TokenInfo which represents the value for the token whitelist HashMap.

[elpiel]

Looks like you have great progress on the task already 🎉
Can you also make sure to include a list of the Changelog in PR so we can later add it to the CHANGELOG.md file.

[elpiel]

After some discussion with Ivo, we came to the following changes:
get_deposit(channel: &Channel, user: &Address) -> Deposit
struct Deposit { total: BigNum, pending: BigNum }

This could change in the future, as we will introduce the UnifiedNum and we have yet to see if we will use the full precision from the validator (BigNum) or directly work with the UnifiedNum from the Adapter onward.

[elpiel]

Can you also make sure to fix the gitmodule

[elpiel]

TODO:

• get_deposit of Dummy adapter

[samparsky]

to make tests reproducible we can create a ganache snapshot of the required deployments and use it on startup

[elpiel]

This is a cool idea for enhancement!
How can we do that?