Make support for "after column"

[Casperhr]

Missing feature

ALTER TABLE `listings` ADD `client_id` INT NULL DEFAULT NULL AFTER `object_no`;

[tanner0101]

Looks neither SQLite or PostgreSQL actually support this. Should probably be added using the DatabaseSchema storage and specific extensions on SchemaBuilder where database type is MySQL.

[tanner0101]

Had to get this one done before it turned a year old ;)

CustomOrder.swift

struct CustomOrder: MySQLModel {
    var id: Int?
    var a: Int
    var b: Int
}

CreateCustomOrder.swift

struct CreateCustomOrder: MySQLMigration {
    static func prepare(on conn: MySQLConnection) -> Future<Void> {
        return MySQLDatabase.create(CustomOrder.self, on: conn) { builder in
            builder.field(for: \.id)
            builder.field(for: \.a)
        }
    }
    
    static func revert(on conn: MySQLConnection) -> Future<Void> {
        return MySQLDatabase.delete(CustomOrder.self, on: conn)
    }
}

struct AddColumnBToCustomOrder: MySQLMigration {
    static func prepare(on conn: MySQLConnection) -> Future<Void> {
        return MySQLDatabase.update(CustomOrder.self, on: conn) { builder in
            builder.field(for: \.b)
            builder.order(\.b, after: \.id)
        }
    }
    
    static func revert(on conn: MySQLConnection) -> Future<Void> {
        return MySQLDatabase.update(CustomOrder.self, on: conn) { builder in
            builder.deleteField(for: \.b)
        }
    }
}

This will be available in 3.0.0 RC 4.1