MM-22707: improved image upload tests and logging (#14018)

* improved image upload tests and error logging message

Signed-off-by: Gabriel Linden Sagula <gsagula@gmail.com>

* removed unecessary logging message

Signed-off-by: Gabriel Linden Sagula <gsagula@gmail.com>

* fixed null ptr issue

Signed-off-by: Gabriel Linden Sagula <gsagula@gmail.com>

* rolled back pointer to the client

Signed-off-by: Gabriel Linden Sagula <gsagula@gmail.com>

* added hexdump of the previewer file

Signed-off-by: Gabriel Linden Sagula <gsagula@gmail.com>

* fixed tests that use the renamed files

Signed-off-by: Gabriel Linden Sagula <gsagula@gmail.com>

* addressed reviewer notes

Signed-off-by: Gabriel Linden Sagula <gsagula@gmail.com>

* addressed reviewer concerns

Signed-off-by: Gabriel Linden Sagula <gsagula@gmail.com>

Co-authored-by: mattermod <mattermod@users.noreply.github.com>

app/post_metadata_test.go

@@ -2181,7 +2181,7 @@ func TestParseImages(t *testing.T) {
 			},
 		},
 		"tiff": {
-			FileName: "test.tiff",
+			FileName: "test_compressed_tiff.tiff",
 			Expected: (*model.PostImage)(nil),
 		},
 		"not an image": {