sql/pgwire: set options based on "options" url parameter

[rafiss]

The PGJDBC docs describe how one can include a URL parameter of options in order to set session variables: https://jdbc.postgresql.org/documentation/head/connect.html#connection-parameters

This is important because PGJDBC does not allow one to set session variables directly in the URL. That is, you need to specify like this:

postgresql://user@host:port/database?options=-c%20serial_normalization=virtual_sequence

and not this

postgresql://user@host:port/database?serial_normalization=virtual_sequence

However, CockroachDB only recognizes the latter right now. The connection initialization in parseClientProvidedSessionParameters
needs to be updated to look for the options key.

---

here's an example that can be used to repro and write a test. the test for this can go in pkg/sql/pgwire/conn_test.go. The test TestConnMessageTooBig has better examples that show how to use pgx and the test/assertion libraries.

    config, err := pgx.ParseConnectionString("postgresql://root@localhost:26257/defaultdb?sslmode=disable&options=-c%20serial_normalization=virtual_sequence")
    if err != nil {
        log.Fatal("error configuring the database: ", err)
    }

    conn, err := pgx.Connect(config)
    if err != nil {
        log.Fatal("error connecting to the database: ", err)
    }
    defer conn.Close(context.Background())

    row, err := conn.QueryRow(context.Background(), "SHOW serial_normalization")
    if err != nil {
        log.Fatal(err)
    }

    var s string
    if err := rows.Scan(&s); err != nil {
        log.Fatal(err)
    }
    // assert s == "virtual_sequence" here
    fmt.Printf("%s \n", s)

[mneverov]

hi, I'd like to work on this.

[rafiss]

@mneverov thanks for your interest! please go ahead. the issue description should have enough pointers to get started :)