Add nextOrThrow method to KiwiJdbc to advance a ResultSet or throw exception

[sleberknight]

Add a simple nextOrThrow(ResultSet) method to KiwiJdbc which advances a ResultSet, or throws an IllegalStateException if the ResultSet#next method returns false. It could also have overloads to accept a message, or a template and parameters.

While trivial, this is useful in certain situations, for example when you execute a "count" query or find a record by (unique) primary key, there should always be exactly one row, and if not then something went wrong (or horribly wrong if you got an empty result set from a "count" query).

Without this (trivial) method, it's easy to see code like:

// after executing a query to find a 'user' record by primary key...
rs.next();

// if above returns false, nothing happens until...

// use the ResultSet to map into an object, e.g.
var user = User.builder()
    .id(rs.getLong("id"))    // ...an exception is thrown here!
    .username(rs.getString("username"))
    //  set more properties...
    .build();

In the above, if rs.next() returns false, you won't see any error until later, when you attempt to access data, in the above when attempting to get the "id" field value. It's better to make the assertion and fail earlier, e.g.

// after executing a query to find a 'user' record by primary key...
nextOrThrow(rs, "user not found with id {}", id);

// use the ResultSet to map into an object, e.g.
var user = User.builder()
    .id(rs.getLong("id"))
    .username(rs.getString("username"))
    //  set more properties...
    .build();

Now an exception is thrown by nextOrThrow with a nicer error message: "user not found with id: 42"