Write service level tests

[bladyjoker]

COOP relies on a single Publisher gRpc service that relies on 2 backend services FactStatementStore and TxBuilder. All these service require a prelude of setting up and it would be quite reassuring to have tests implemented at the Publisher level.

1. Prelude FactStatementStore

• Setup Sqlite db and run the gRpc service

2. Prelude TxBuilder

• Setup the Plutip local cluster and initialize the entire COOP system followed by running a TxBulder

3. Run Publisher

Once the Publisher is active, we can write tests to ensure the entire stack works as intended:

1. Publishing a Fact Statement
2. Publishing a Fact Statement that has already been published
3. Publishing a Fact Statement that doesn't exist in the store
4. Garbage collection scenarios...