Handle relative <link> elements in Atom parser — use xml:base when present to resolve. Add test case.

Modules/Parser/Tests/ParserTests/AtomParserTests.swift

@@ -109,4 +109,22 @@ final class AtomParserTests: XCTestCase {
 			XCTAssertNotEqual(article.title, "Default Title")
 		}
 	}
+
+	func testLinkElementsWithRelativeURLs() {
+
+		// This feed has <link> elements that look like this…
+		//		<link href="/en/publish/2022/07/01/great-moments-in-document-history-reimagining-the-declaration-of-independence-as-pdf"/>
+		// …and it also has, in the feed declaration…
+		// 		xml:base="https://blog.adobe.com"
+		// …and so the <link> values should be parsed as (for example):
+		// https://blog.adobe.com/en/publish/2022/07/01/great-moments-in-document-history-reimagining-the-declaration-of-independence-as-pdf
+		// Issue: https://github.com/Ranchero-Software/NetNewsWire/issues/3662
+
+		let d = parserData("adobe", "atom", "https://blog.adobe.com/feed.xml")
+		let parsedFeed = try! FeedParser.parse(d)!
+
+		for article in parsedFeed.items {
+			XCTAssertTrue(article.url!.hasPrefix("https://blog.adobe.com/en/publish/20"))
+		}
+	}
 }