Add schema.org markup to SEO-enabled posts (#36075)

app/lib/seo/adapter.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+class SEO::Adapter < ActiveModelSerializers::Adapter::Base
+  def self.default_key_transform
+    :camel_lower
+  end
+
+  def self.transform_key_casing!(value, _options)
+    SEO::CaseTransform.camel_lower(value)
+  end
+
+  def serializable_hash(options = nil)
+    serialized_hash = serializer.serializable_hash(serialization_options(options))
+    self.class.transform_key_casing!(serialized_hash, instance_options)
+  end
+end

app/lib/seo/case_transform.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+module SEO::CaseTransform
+  PREFIX_KEYS = %w(
+    context
+    id
+    type
+  ).freeze
+
+  class << self
+    def camel_lower_cache
+      @camel_lower_cache ||= {}
+    end
+
+    def camel_lower(value)
+      case value
+      when Array
+        value.map { |item| camel_lower(item) }
+      when Hash
+        value.deep_transform_keys! { |key| camel_lower(key) }
+      when Symbol
+        camel_lower(value.to_s).to_sym
+      when String
+        camel_lower_cache[value] ||= begin
+          if PREFIX_KEYS.include?(value.to_s)
+            "@#{value}"
+          else
+            value.underscore.camelize(:lower)
+          end
+        end
+      else
+        value
+      end
+    end
+  end
+end