Postgresql stored columns, and overrides #303

Hello, I've been trying out sqlc, I discovered a couple of bugs, when looking if I could replace my current DB layer with a sqlc generated one. As I much prefer writing sql.

Apart from the need for #276 which I will be watching. The only outstanding issues are related to the way I must handle timestamps.

Keeping nano timestamp precision with Postgresql requires first storing that data into an bigint, I then use a computed column, this is simply for readability when querying the tables manually. A sample can be seen below: (i've ** the important line)

CREATE TABLE trades.currency_rates (
   timestamp_nanos  BIGINT PRIMARY KEY,
   **timestamp        TIMESTAMP GENERATED ALWAYS AS (to_timestamp(timestamp_nanos/1000000000.0)) STORED,**
   base             CHAR(10) NOT NULL,
   quote            CHAR(10) NOT NULL
);

This causes the following error

schema.sql:1:1: syntax error at or near "("
If I removed the STORED column, everything works as expected.

I will also need to ignore this column so its not included in the generated structs. Would you consider allowing overrides to achieve this with something like
"overrides": [ { "column": "*.timestamp", "filter": "ignore" } ]

The other bug I found was related to overrides which displays this error

error parsing sqlc.json: Package override go_type specifier "time.Time" is not the proper format, expected 'package.type', e.g. 'github.com/segmentio/ksuid.KSUID'

"overrides": [ { "column": "currency_rates.timestamp_nanos", "go_type": "time.Time" } ]
What i actually need to be able to do is use a wildcard (match any table) to automatically convert a data type using a function, such as:

"overrides": [ { "column": "*.timestamp_nanos", "go_function": "time.Unix(0, sqlc.(TimestampNanos)).UTC()" } ]

If I were to spend time looking to implement these features, would this be something you would consider merging?