Add support for custom pre-functions in transformation (wasm/remote). (#162)

Author: nitzanj

cloudinary-core/src/main/java/com/cloudinary/Transformation.java

@@ -893,4 +893,13 @@ public T variables(Expression... variables) {
     public T customFunction(CustomFunction action) {
         return param("custom_function", action.toString());
     }
+
+    /**
+     * Set a custom pre-function, such as a call to a lambda function or a web-assembly function.
+     * @param action The custom action to perform, see {@link CustomFunction}.
+     * @return The transformation for chaining
+     */
+    public T customPreFunction(CustomFunction action) {
+        return param("custom_function", "pre:" + action.toString());
+    }
 }

cloudinary-core/src/test/java/com/cloudinary/test/CloudinaryTest.java

@@ -1163,6 +1163,13 @@ public void testCustomFunction(){
                 new Transformation().customFunction(remote("https://df34ra4a.execute-api.us-west-2.amazonaws.com/default/cloudinaryFunction")).generate());
     }
 
+    @Test
+    public void testCustomPreFunction(){
+        assertEquals("fn_pre:wasm:blur_wasm", new Transformation().customPreFunction(wasm("blur_wasm")).generate());
+        assertEquals("fn_pre:remote:aHR0cHM6Ly9kZjM0cmE0YS5leGVjdXRlLWFwaS51cy13ZXN0LTIuYW1hem9uYXdzLmNvbS9kZWZhdWx0L2Nsb3VkaW5hcnlGdW5jdGlvbg==",
+                new Transformation().customPreFunction(remote("https://df34ra4a.execute-api.us-west-2.amazonaws.com/default/cloudinaryFunction")).generate());
+    }
+
     public static Map<String, String> getUrlParameters(URI uri) throws UnsupportedEncodingException {
         Map<String, String> params = new HashMap<String, String>();
         for (String param : uri.getRawQuery().split("&")) {