oAuthAccessTokenSubscriber.swift

self.subscriptions["oAuthAccessTokenSubscriber"] =
    self.oAuthAccessTokenPublisher(temporaryCredentials: temporaryCredentials,
                                   verifier: oAuthVerifier) // 1
    .receive(on: DispatchQueue.main) // 2
    .sink(receiveCompletion: { _ in // 3
        // Error handler
    }, receiveValue: { [weak self] (tokenCredentials, user) in // 4
        guard let self = self else { return }
        
        // 5
        self.subscriptions.removeValue(forKey: "oAuthRequestTokenSubscriber")
        self.subscriptions.removeValue(forKey: "onOAuthRedirect")
        self.subscriptions.removeValue(forKey: "oAuthAccessTokenSubscriber")
        
        self.tokenCredentials = tokenCredentials // 6
        self.user = user // 7
    })