New "Saint George" status effect, Enderman trading

This idea is to add a new status effect to Minecraft, called "Saint George" (or any other alternative mythical Dragon Slayer), acquired whenever the Ender Dragon is killed.

If a player has this status effect, looking at an Enderman will not provoke it into attacking the player.

Furthermore, a player with this status effect can trade with Endermen.

To make a trade with an Enderman, the player holds "money" in his main hand, and a "signifier" in his off hand, and looks an Enderman in the eyes.

If this Enderman thinks that this is enough money for a trade, it will hold out in its hands whatever the trade result would be.  Right clicking on the Enderman will cause the player's money to be consumed and the item in the Enderman's hands to be given to the player.

For most signifiers, the item which the Enderman will trade to the player is the same as the player... for example, End Stone, Chorus Flowers, Magenta Stained Glass.

For other signifiers, the Enderman will take the signifier along with the payment, and give the player something different.  For example, leather might become a nametag, a book might become a randomly enchanted book, etc

If the Enderman is holding a block in his hands, a player with the Saint George status effect can pay him to teleport to wherever he picked it up from, and put it back down.

The money would be popped chorus fruit.

The duration of the Saint George status effect (Initially MAX_INT) would halved whenever the player changes dimension or hurts an Enderman.