Cover `joinedTheRightTeam` with a test

[HerbCaudill]

In the Connection protocol, we confirm that we haven't been spoofed into joining the wrong team: Once we've joined and gotten the full team history, we look for an invitation matching the secret invitation code we were given.

auth/packages/auth/src/connection/Connection.ts

Lines 605 to 613 in 34c4059

	joinedTheRightTeam: (context, event) => {
	// Make sure my invitation exists on the signature chain of the team I'm about to join.
	// This check prevents an attack in which a fake team pretends to accept my invitation.
	const { payload } = event as AcceptInvitationMessage
	const { serializedGraph, teamKeyring } = payload
	const state = getTeamState(serializedGraph, teamKeyring)
	const { id } = this.myProofOfInvitation(context)
	return select.hasInvitation(state, id)
	},

This looks right but there are currently no tests covering this scenario.