Implement parsing of the <id> element in OPDS 1.x feeds (#655)

Author: x0000ff

Sources/OPDS/OPDS1Parser.swift

@@ -93,6 +93,8 @@ public class OPDS1Parser: Loggable {
         }
         let feed = Feed(title: title)
 
+        feed.metadata.identifier = root.firstChild(tag: "id")?.stringValue
+
         if let tmpDate = root.firstChild(tag: "updated")?.stringValue,
            let date = tmpDate.dateFromISO8601
         {

Sources/Shared/OPDS/OpdsMetadata.swift

@@ -9,6 +9,7 @@ import Foundation
 /// OPDS metadata properties.
 public class OpdsMetadata {
     public var title: String
+    public var identifier: String?
     public var numberOfItem: Int?
     public var itemsPerPage: Int?
     public var currentPage: Int?

Tests/OPDSTests/readium_opds1_1_test.swift

@@ -46,6 +46,7 @@ class readium_opds1_1_test: XCTestCase {
     }
 
     func testMetadata() {
+        XCTAssert(feed!.metadata.identifier == "urn:uuid:433a5d6a-0b8c-4933-af65-4ca4f02763eb")
         XCTAssert(feed!.metadata.title == "Unpopular Publications")
         // TODO: add more tests...
     }