🍾 Implement schema support

Breaking change

Aliases syntax has been changed

was

let u = User.as("u")
u~\.$id

became

let u = User.as("u")
u.$id

Schema

schema for postgres is the same as database for mysql.

How to declare some schema

struct Deleted: Schemable {
    static var schemaName: String { "deleted" }
}

or right into your model (example for Bridges)

final class DeletedUser: Table, Schemable {
    static var schemaName: String { "deleted" }
    static var tableName: String { "user" }
    
    @Column("id")
    var id: UUID

    @Column("email")
    var email: String
}

Usage examples

// if `User` model conforms to `Schemable` it will use `public` schema all the time
\User.$id // result: "public"."user"."id"

// otherwise it will be printed simply without any schema
\User.$id // result: "user"."id"

// `DeletedUser` model conforms to `Schemable` and has custom schema name
\DeletedUser.$id // result: "deleted"."user"."id"

// Alternatively we can wrap any model to any schema
User.inSchema("deleted").$id // result: "deleted"."user"."id"

// also we can use aliases with tables with schemas
DeletedUser.as("du") // result: "deleted"."user" as "du"
// or
User.inSchema("deleted").as("du") // result: "deleted"."user" as "du"

New alias features

let u = User.as("u")

// to reach \User.$id we now can simply call
u.$id // result: "u"."id"

// the same for aliases with schemas
// declare aliases easily
let hu = User.inSchema("hello").as("hu")
// or even
struct HelloSchema: Schemable {
    static var schemaName: String { "hello" }
}
let hu = User.inSchema(HelloSchema.self).as("hu")

// use alias as table
hu.table // result: "hello"."user" as "hu"

// or simply call its columns
hu.$id // result: "hu"."id"

Custom aliases for subqueries

let u = SwifQLAlias("u")
let subQueryWithAlias = |SwifQL.select(User.table.*).from(User.table)| => u
// result: (SELECT "hello"."user".* FROM "hello"."user") as "u"

// and then also use its paths easily
u.id // result: "u"."id"
// even with any fantasy columns
u.heeeeey // result: "u"."heeeeey"