(feat): Unpack extensions into complex function types #8

The more in-depth we use extensions, the more likely is is that we need custom extensions. New `UnpackExtensions` function in the high package makes this easy. Low level models have been updated to support feature fully and docs added in README and examples as well.

Signed-off-by: Dave Shanley <dave@quobix.com>

datamodel/low/v2/response_test.go

@@ -110,4 +110,5 @@ headers:
 
 	// hash
 	assert.Equal(t, n.Hash(), n2.Hash())
+	assert.Len(t, n.GetExtensions(), 1)
 }