Add RequestEventData for saving request events

[Karlatemp]

close #1145

[Him188]

如果设计为每个事件一种 Ticket (或是更好的名称) 是否更好? 名称更精简

public sealed interface EventTicket {
    public val botId: Long
}

@Serializable
public class MemberInvitationTicket(
    public override val botId: Long,
    public val groupId: Long,
    public val eventId: Long,
    public val invitorId: Long,
    public val groupName: String,
    public val invitorNick: String,
)  : EventTicket

public data class BotInvitedJoinGroupRequestEvent { 
    public fun createTicket(): MemberInvitationTicket = TODO()
}

用户如果以 MemberInvitationTicket 类型序列化, 则会直接使用 MemberInvitationTicket 的 serializer. 而如果使用 EventTicket, 用户可以选择使用 contextual serializer 或 polymorphic serializer