Enforce Committer when entering Transactions

At the moment there's a field on `envelopes.Transaction` to capture who was the one who entered the transaction data, but it's virtually always. `baronial` should start allowing user name and email information to be stored as config, and apply it to transactions that are created by that user.

Locate the configuration path and the code that creates envelopes.Transaction. Add configurable user name and email values, then verify that transactions created by that user store the committer information. Done means both values can be configured and are applied to newly created transactions.

Written by the indexing model from the issue text.