Allow modification of existing permissions in ChannelAction

Inspired by discord/discord-api-docs#2520

General Troubleshooting

• I have checked for similar issues.
• I have updated to the [latest JDA version][download].
• I have checked the branches or the maintainers’ PRs for upcoming features.

Feature Request

I would like a way to view and update existing permission overrides from a ChannelAction object.

Example Use-Case

Because of discord/discord-api-docs#2520, when using JDA’s Category#createVoiceChannel you must now sanitise out all MANAGE_ROLES permissions unless the bot is given admin permissions. Currently I’m just using this as a quick hack, which is not ideal:

private object JDAHack {
  lazy val field: Field = {
    val f = classOf[ChannelActionImpl[_]].getDeclaredField("overrides")
    f.setAccessible(true)
    f
  }

  def removeManageRolesPerms(channelReq: ChannelAction[_]): Unit = {
    try {
      val overrides = field.get(channelReq).asInstanceOf[TLongObjectHashMap[PermOverrideData]]
      overrides.transformValues { v =>
        val manageRoles = Permission.MANAGE_ROLES.getRawValue
        new PermOverrideData(v.`type`, v.id, v.allow & ~manageRoles, v.deny & ~manageRoles)
      }
    } catch {
      case NonFatal(_) =>
    }
  }
}

[ScoreUnder]

I considered those, but using createVoiceChannel on the guild leaves me the problem of not taking permissions from the category (e.g. voice ban and priority speaker roles), and replacing with addPermissionOverride requires that I know exactly which permissions have that kill-bit in them in the first place.

[MinnDevelopment]

You can also use ChannelAction#addPermissionOverride to replace existing overrides.