Add support for catalog roles

[Flgado]

This PR adds support for specifying catalog roles in the Trino Go client via both the DSN string and the Config struct. Roles are passed as either:

• A map[string]string mapping catalogs to roles (e.g. {"hive": "analyst", "system": "admin"})

The roles are URL-encoded and appended to the DSN as a colon-separated list of catalog=ROLE{role} entries.

Example

// Using role map
c := &Config{
    ServerURI: "https://user@localhost:8080",
    Roles: map[string]string{"hive": "analyst", "system": "admin"},
}

using directly the dns connection

dns := ...?roles=catalog1:role1;catalog2:role2

[nineinchnick]

@Flgado would you like to get back to this?

[Flgado]

@nineinchnick Sure! I’m a bit busy these days, but I can pick this up in the next few days. 👍🏻

[Flgado]

@nineinchnick, do we want to support the X-Trino-Role header when it's provided as a named argument?

For example: db.Query("SELECT * FROM foobar WHERE id = ?", 1, sql.Named("X-Trino-Role", ...))

If so, that should overwrite the roles on the connection string ?
Can this be a security concern ?

[nineinchnick]

We can allow it, and it's not a security concern. The same program that creates the db connection executes the queries. It would be a good workaround for the unsupported SET ROLE query - we don't handle the X-Trino-Set-Role header in server responses.

[Flgado]

@nineinchnick can you take a look ?
I am not sure if a argName we should pass the roles as catalog:role1;catalog2:role2 like it is on dsn. Let me know what you think :)