Proto/CLST: deposit tez

What

Adds the FA2 ledger for single asset in the storage, which is minted from transfers

Why

How

• TODO:

• Fix existing generic tests, or

• Replace them with more specific tests

• Adds some combinator functions to build entrypoints

• Change the type of CLST storage to be only a ledger for now, and no parameter.

• Add the implementation of the contract: an entrypoint deposit accepting tez and Unit as parameter. When it receives some tez, allocates the same amount of tokens in its storage to the sender.

Manually testing the MR

Run a sandbox, then:

octez-client --wait none transfer 100 from bootstrap1 to KT1WCsbJx996ebZfutAitHYsZ8FUZFsTdaD7 --entrypoint "deposit" --burn-cap 10

You should see in the receipt that a new bigmap entry has been created, associating 100000000 "clst" (mutez) to bootstrap1 (byte encoding of its address).

      Updated big_maps:
        New map(4) of type (big_map address nat)
        Set map(4)[0x000002298c03ed7d454a101eb7022bc95f7e5f41ac78] to 100000000

Bake, retransfer the same amount again, and now it should be 200000000.

Voilà, you now have a contract that receives tez and handle them in a ledger.

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR