Add BuildContact and CRUD functionality for contacts

[fourjr]

This functionality does not work on all WhatsApp mobile apps. I suggest testing using a WhatsApp desktop client as the contact changes are reflected there.

Example Usage

// add or edit contact
client.SendAppState(appstate.BuildContact(v.Info.Sender, "Full Name"))
// remove contact
client.SendAppState(appstate.RemoveContact(v.Info.Sender))

[AlejandroPerez92]

That is awesome! It could probably prevent some bans

[purpshell]

looks pretty good to me

[devlikepro]

Idk how for others, but I'd expect method RemoveContact to actually "remove the contact".

For consistency with other methods, we could apply the changes, so the function name makes sense, because it actually "builds remove contact" data - so BuildRemoveContact

The same for BuildAddContact

Or even

• BuildAddContactPatch
• BuildRemoveContactPatch

a bit wordy, but show what the methods actually do

[devlikepro]

Suggested change

	func BuildContact(target types.JID, fullName string) PatchInfo {
	func BuildAddContact(target types.JID, fullName string) PatchInfo {

OR

Suggested change

	func BuildContact(target types.JID, fullName string) PatchInfo {
	func BuildAddContactPatch(target types.JID, fullName string) PatchInfo {

[devlikepro]

Suggested change

	func RemoveContact(target types.JID) PatchInfo {
	func BuildRemoveContact(target types.JID) PatchInfo {

OR

Suggested change

	func RemoveContact(target types.JID) PatchInfo {
	func BuildRemoveContactPatch(target types.JID) PatchInfo {

[huzairuje]

nice to have and i am abit lost when something with contacts management, LGTM