privacy: add function to strip location data from photos

Add a function to strip GPS data from images before uploading to
hosting service.

Lightning-address: kernelkind@getalby.com
Signed-off-by: kernelkind <kernelkind@gmail.com>
Signed-off-by: William Casarin <jb55@jb55.com>

damusTests/ImageMetadataTest.swift

@@ -0,0 +1,43 @@
+//
+//  LocationStrippingTest.swift
+//  damusTests
+//
+//  Created by KernelKind on 2/8/24.
+//
+
+import XCTest
+@testable import damus
+
+final class ImageMetadataTest : XCTestCase {
+    func testRemoveGPSData() {
+        let bundle = Bundle(for: type(of: self))
+        guard let imageURL = bundle.url(forResource: "img_with_location", withExtension: "jpeg"),
+                let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first 
+        else {
+            XCTFail("Failed to load test image from bundle")
+            return
+        }
+
+        let testOutputURL = documentsDirectory.appendingPathComponent("img_with_location.jpeg")
+        do {
+            if FileManager.default.fileExists(atPath: testOutputURL.path) {
+                try FileManager.default.removeItem(at: testOutputURL)
+            }
+            try FileManager.default.copyItem(at: imageURL, to: testOutputURL)
+        } catch {
+            XCTFail("Setup failed: Unable to copy test image to documents directory - \(error)")
+            return
+        }
+
+        let removalSuccess = removeGPSDataFromImage(fromImageURL: testOutputURL)
+
+        XCTAssertTrue(removalSuccess, "GPS data removal was not successful")
+
+        guard let sourceAfterRemoval = CGImageSourceCreateWithURL(testOutputURL as CFURL, nil),
+              let imagePropertiesAfterRemoval = CGImageSourceCopyPropertiesAtIndex(sourceAfterRemoval, 0, nil) as? [String: Any],
+              imagePropertiesAfterRemoval[kCGImagePropertyGPSDictionary as String] == nil else {
+            XCTFail("GPS data was not removed from the image")
+            return
+        }
+    }
+}