Adds examples of accessing CE extensions in functions (#392)

Author: jmcx

docs/transformation/functions/nodejsfunctions.md

@@ -14,12 +14,19 @@ spec:
   ceOverrides:
     extensions:
       type: io.triggermesh.nodejs.sample
-  entrypoint: transformName
+  entrypoint: handler
   code: |
-    module.exports.transformName = async (event) => {
+    exports.handler = async function(event, context) {
+  
       if (event.name == "") {
-        event.name = "placeholder";
+        event.name = "placeholder"; # (1)
       }
+      
+      console.log(context.clientContext.custom["foo"]) # (2)
       return event;
     };
 ```
+
+1.  Tests if the event.name property has a value, if not sets it to placeholder.
+2.  Logs the value of a CloudEvents extension attribute called "foo". To pass an extension attribute called foo in a request using curl, use -H "ce-foo: bar".
+

docs/transformation/functions/pythonfunctions.md

@@ -27,14 +27,18 @@ spec:
   runtime: python
   adapterOverrides:
     public: true
-  entrypoint: endpoint
+  entrypoint: handler
   code: |
     import json
-    def endpoint(event, context):
+    def handler(event, context):
       jsonEvent = json.loads(event)
-      return "Hello " + jsonEvent['name']
+      print(context.client_context.custom["foo"]) # (1)
+      return "Hello " + jsonEvent['name'] # (2)
 ```
 
+1.  Logs the value of a CloudEvents extension attribute called "foo". To pass an extension attribute called foo in a request using curl, use -H "ce-foo: bar".
+2.  Returns "Hello" followed by the value of the name attribute in the event message 
+
 You can then create the function with:
 
 ```console

docs/transformation/functions/rubyfunctions.md

@@ -14,10 +14,14 @@ spec:
   ceOverrides:
     extensions:
       type: io.triggermesh.ruby.sample
-  entrypoint: endpoint
+  entrypoint: handler
   code: |
-    def endpoint(event:, context:)
+    def handler(event:, context:)
+    puts context.client_context["custom"]["foo"] # (1)
     hash = {date: Time.new}
-    { statusCode: 200, body: JSON.generate(hash) }
+    { statusCode: 200, body: JSON.generate(hash) } (2)
     end
 ```
+
+1.  Logs the value of a CloudEvents extension attribute called "foo". To pass an extension attribute called foo in a request using curl, use -H "ce-foo: bar".
+2.  returns the current time