fix(search): take the photo iso from exif:IsoSpeedRatings

Base ISO is a Canon maker note tag holding Canon's raw encoded value, not the iso of the shot: other cameras got no iso, Canon photos a wrong one (256 for an ISO 800 shot). exif:IsoSpeedRatings is there on tika 3 and tika 4.

services/search/pkg/content/tika_photo.go

@@ -40,7 +40,7 @@ func (t Tika) getPhoto(meta map[string][]string) *libregraph.Photo {
 		}
 	}
 
-	if v, err := getFirstValue(meta, "Base ISO"); err == nil {
+	if v, err := getFirstValue(meta, "exif:IsoSpeedRatings"); err == nil {
 		if i, err := strconv.ParseInt(v, 0, 32); err == nil {
 			initPhoto()
 			photo.SetIso(int32(i))

services/search/pkg/content/tika_photo_test.go

@@ -16,7 +16,7 @@ var _ = Describe("getPhoto", func() {
 			"exif:ExposureTime":     {"0.001"},
 			"exif:FNumber":          {"1.8"},
 			"exif:FocalLength":      {"50"},
-			"Base ISO":              {"100"},
+			"exif:IsoSpeedRatings":  {"100"},
 			"tiff:Orientation":      {"1"},
 			"exif:DateTimeOriginal": {"2018-01-01T12:34:56"},
 		})
@@ -32,6 +32,16 @@ var _ = Describe("getPhoto", func() {
 		Expect(photo.TakenDateTime).To(Equal(libregraph.PtrTime(time.Date(2018, 1, 1, 12, 34, 56, 0, time.UTC))))
 	})
 
+	It("takes the iso of the shot, not the canon maker note base iso", func() {
+		photo := Tika{}.getPhoto(map[string][]string{
+			"exif:IsoSpeedRatings": {"800"},
+			"Base ISO":             {"256"},
+			"img:Base ISO":         {"256"},
+		})
+		Expect(photo).ToNot(BeNil())
+		Expect(photo.Iso).To(Equal(libregraph.PtrInt32(800)))
+	})
+
 	It("returns nil when no photo metadata is present", func() {
 		Expect(Tika{}.getPhoto(map[string][]string{})).To(BeNil())
 	})