First pass at documenting error rendering

source/guides/serialization/errors.html.md

@@ -1,8 +1,54 @@
 ---
 layout: guides
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-# Serialization
+# Serialization - Rendering errors
 
-## Rendering errors
+You can also use jsonapi-rb to render JSON API errors.
+
+## Plain ruby
+
+When using jsonapi-rb in plain ruby (or from within a framework outside of a
+controller), you can render an errors document as follows:
+
+```ruby
+JSONAPI::Serializable::ErrorRenderer.render([
+  JSONAPI::Serializable::Error.create({
+    status: "422",
+    source: { pointer: "/data/attributes/first-name" },
+    title:  "Invalid Attribute",
+    detail: "First name must contain at least three characters."
+  })
+])
+```
+
+## Ruby on Rails
+
+When using jsonapi-rb with Rails (via the jsonapi-rails gem), rendering errors is done
+via the usual `render` controller method by using the `jsonapi_errors` renderer:
+
+```ruby
+render jsonapi_errors: {
+  status: "422",
+  source: { "pointer": "/data/attributes/volume" },
+  detail: "Volume does not, in fact, go to 11."
+}
+```
+
+You can also pass `ActiveModel::Errors`
+
+```ruby
+render jsonapi_errors: post.errors
+```
+
+or you can pass an array of objects
+
+```ruby
+render jsonapi_errors: [post.errors, author.errors, {
+  status: "400",
+  detail: "JSON parse error - Expecting property name at line 1 column 2 (char 1)."
+}]
+```
+
+## Hanami
 
 Soon.