Expanded documentation

Author: Daeda88

README.md

@@ -185,6 +185,44 @@ In combination with a `SerialName` specified for the child class, you have full
 }
 ```
 
+<h4>Serialization of Updates</h4>
+Firestore contains update methods that allow for multiple fields to be updated at the same time. 
+This sdk offers special update methods that allow for applying custom serialization to each individual field though an update builder.
+Where an `update` method exists, an `updateFields` method will also be available. In this, each value can have its serializer customized:
+
+```kotlin
+documentRef.updateFields {
+    "field" to "value"
+    // Set the value of otherField to "1" using a custom Serializer
+    "otherField".to(IntAsStringSerializer(), 1)
+    
+    // Overwrite build settings. All fields added after this will have these build settings applied
+    buildSettings = {
+        encodeDefaults = true
+        serializersModule = module
+    }
+    "city" to abstractCity
+}
+```
+
+Similarly, the `Query` methods `startAt`/`startAfter`/`endAt`/`endBefore` have an alternative method in `startAtFieldValues`/`startAfterFieldValues`/`endAtFieldValues`/`endBeforeFieldValues`
+
+```kotlin
+query.orderBy("field", "otherField", "city").startAtFieldValues { // similar syntax for startAfter/endAt/endBefore
+    add("Value")
+
+    // Starts at "1" for the otherField value
+    add(1, IntAsStringSerializer())
+
+    // Overwrite build settings. All field values added after this will have these build settings applied
+    buildSettings = {
+        encodeDefaults = true
+        serializersModule = module
+    }
+    add(abstractCity)
+}
+```
+
 <h3><a href="https://kotlinlang.org/docs/reference/functions.html#default-arguments">Default arguments</a></h3>
 
 To reduce boilerplate, default arguments are used in the places where the Firebase Android SDK employs the builder pattern:
@@ -239,20 +277,6 @@ citiesRef.where {
 }
 ```
 
-Similar methods exist for `update`/`startAt`/`startAfter`/`endAt`/`endBefore` methods in the Firestore module:
-
-```kotlin
-documentRef.update {
-    "field" to "value"
-    "otherField".to(IntAsStringSerializer(), 1)
-}
-
-query.orderBy("field", "otherField").startAt { // similar syntax for startAfter/endAt/endBefore
-    add("Value")
-    add(1, IntAsStringSerializer())
-}
-```
-
 <h3><a href="https://kotlinlang.org/docs/reference/operator-overloading.html">Operator overloading</a></h3>
 
 In cases where it makes sense, such as Firebase Functions HTTPS Callable, operator overloading is used: