Add bolt11 parser and Invoice View

Changelog-Added: Display bolt11 invoice widgets on posts

damusTests/InvoiceTests.swift

@@ -0,0 +1,38 @@
+//
+//  InvoiceTests.swift
+//  damusTests
+//
+//  Created by William Casarin on 2022-10-18.
+//
+
+import XCTest
+@testable import damus
+
+final class InvoiceTests: XCTestCase {
+
+    override func setUpWithError() throws {
+        // Put setup code here. This method is called before the invocation of each test method in the class.
+    }
+
+    override func tearDownWithError() throws {
+        // Put teardown code here. This method is called after the invocation of each test method in the class.
+    }
+
+    func testParseInvoice() throws {
+        let invstr = "lnbc100n1p357sl0sp5t9n56wdztun39lgdqlr30xqwksg3k69q4q2rkr52aplujw0esn0qpp5mrqgljk62z20q4nvgr6lzcyn6fhylzccwdvu4k77apg3zmrkujjqdpzw35xjueqd9ejqcfqv3jhxcmjd9c8g6t0dcxqyjw5qcqpjrzjqt56h4gvp5yx36u2uzqa6qwcsk3e2duunfxppzj9vhypc3wfe2wswz607uqq3xqqqsqqqqqqqqqqqlqqyg9qyysgqagx5h20aeulj3gdwx3kxs8u9f4mcakdkwuakasamm9562ffyr9en8yg20lg0ygnr9zpwp68524kmda0t5xp2wytex35pu8hapyjajxqpsql29r"
+        let parsed = parse_mentions(content: invstr, tags: [])
+        
+        XCTAssertNotNil(parsed)
+        XCTAssertEqual(parsed.count, 2)
+        XCTAssertEqual(parsed[0].is_text, "")
+        XCTAssertNotNil(parsed[1].is_invoice)
+        guard let invoice = parsed[1].is_invoice else {
+            return
+        }
+        XCTAssertEqual(invoice.amount, 10000)
+        XCTAssertEqual(invoice.expiry, 604800)
+        XCTAssertEqual(invoice.created_at, 1666139119)
+        XCTAssertEqual(invoice.string, invstr)
+    }
+
+}