Debug log when type_code fails to convert to a data_type

[dbeatty10]

resolves #134

Problem

For any given adapter, it's possible that dbt doesn't recognize a data type specified in a dbt model contract. An example is dbt-labs/dbt-postgres#54

In those cases, we want there to be a mechanism for the dbt adapter to emit a log message of what's going on.

Solution

Emit a debug-level log message any time a data type is not recognized within dbt-postgres. That way, users can at least see in the logs what is going on.

Log messages will look like the following:

The type_code 790 was not recognized

An example of how to utilize this log message is within dbt-labs/dbt-postgres#39

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development, and it appears to resolve the stated issue
• This PR includes tests
• This PR has already received feedback and approval from Product or DX

[mikealfare]

I only noticed one thing, which is aesthetic. I'm not super familiar with protobuf, but this change looks consistent with the others.