Swift notification plugin (#436)

* Add Swift notification plugin

* Hash the metadata

* Validate min sendable amount

* Remove initializer as base class, UNNotificationServiceExtension, has no default initializer

* Set the PaymentMethod

* Handle PaymentDetails in SwapUpdated

* Improve payment text

lib/bindings/langs/swift/Sources/BreezSDKLiquid/Task/LnurlPayInvoice.swift

@@ -0,0 +1,56 @@
+import UserNotifications
+import Foundation
+
+struct LnurlInvoiceRequest: Codable {
+    let reply_url: String
+    let amount: UInt64
+}
+
+struct LnurlInvoiceResponse: Decodable, Encodable {
+    let pr: String
+    let routes: [String]
+    
+    init(pr: String, routes: [String]) {
+        self.pr = pr
+        self.routes = routes
+    }
+}
+
+class LnurlPayInvoiceTask : LnurlPayTask {
+    fileprivate let TAG = "LnurlPayInvoiceTask"
+    
+    init(payload: String, logger: ServiceLogger, contentHandler: ((UNNotificationContent) -> Void)? = nil, bestAttemptContent: UNMutableNotificationContent? = nil) {
+        let successNotificationTitle = ResourceHelper.shared.getString(key: Constants.LNURL_PAY_INVOICE_NOTIFICATION_TITLE, fallback: Constants.DEFAULT_LNURL_PAY_INVOICE_NOTIFICATION_TITLE)
+        let failNotificationTitle = ResourceHelper.shared.getString(key: Constants.LNURL_PAY_NOTIFICATION_FAILURE_TITLE, fallback: Constants.DEFAULT_LNURL_PAY_NOTIFICATION_FAILURE_TITLE)
+        super.init(payload: payload, logger: logger, contentHandler: contentHandler, bestAttemptContent: bestAttemptContent, successNotificationTitle: successNotificationTitle, failNotificationTitle: failNotificationTitle)
+    }
+    
+    override func start(liquidSDK: BindingLiquidSdk) throws {
+        var request: LnurlInvoiceRequest? = nil
+        do {
+            request = try JSONDecoder().decode(LnurlInvoiceRequest.self, from: self.payload.data(using: .utf8)!)
+        } catch let e {
+            self.logger.log(tag: TAG, line: "failed to decode payload: \(e)", level: "ERROR")
+            self.displayPushNotification(title: self.failNotificationTitle, logger: self.logger, threadIdentifier: Constants.NOTIFICATION_THREAD_LNURL_PAY)
+            throw e
+        }
+        
+        do {
+            // Get the lightning limits
+            let limits = try liquidSDK.fetchLightningLimits()
+            // Check amount is within limits
+            let amountSat = request!.amount / UInt64(1000)
+            if amountSat < limits.receive.minSat || amountSat > limits.receive.maxSat {
+                throw InvalidLnurlPayError.amount(amount: request!.amount)
+            }
+            let plainTextMetadata = ResourceHelper.shared.getString(key: Constants.LNURL_PAY_METADATA_PLAIN_TEXT, fallback: Constants.DEFAULT_LNURL_PAY_METADATA_PLAIN_TEXT)
+            let metadata = "[[\"text/plain\",\"\(plainTextMetadata)\"]]"
+            let prepareReceivePaymentRes = try liquidSDK.prepareReceivePayment(req: PrepareReceiveRequest(payerAmountSat: amountSat, paymentMethod: PaymentMethod.lightning))
+            let receivePaymentRes = try liquidSDK.receivePayment(req: ReceivePaymentRequest(prepareResponse: prepareReceivePaymentRes, description: metadata, useDescriptionHash: true))
+            self.replyServer(encodable: LnurlInvoiceResponse(pr: receivePaymentRes.destination, routes: []), replyURL: request!.reply_url)
+        } catch let e {
+            self.logger.log(tag: TAG, line: "failed to process lnurl: \(e)", level: "ERROR")
+            self.fail(withError: e.localizedDescription, replyURL: request!.reply_url)
+        }
+    }
+}