Update the specification.md and events.json to make both source and type eventDef properties optional (#678)

Author: cdavernas

schema/events.json

@@ -74,22 +74,21 @@
       "additionalProperties": false,
       "if": {
         "properties": {
-          "kind": {
-            "const": "consumed"
+          "source": {
+            "type": "null"
           }
         }
       },
       "then": {
         "required": [
           "name",
-          "source",
           "type"
         ]
       },
       "else": {
         "required": [
           "name",
-          "type"
+          "source"
         ]
       }
     },

specification.md

@@ -3320,8 +3320,8 @@ It's worth noting that if an [auth definition](#Auth-Definition) has been define
 | Parameter | Description | Type | Required |
 | --- | --- | --- | --- |
 | name | Unique event name | string | yes |
-| source | CloudEvent source | string | yes if kind is set to "consumed", otherwise no |
-| type | CloudEvent type | string | yes |
+| source | CloudEvent source | string | no if `type` is set, otherwise yes. If not set when `kind` is `produced`, runtimes are expected to use a default value, such as https://serverlessworkflow.io in order to comply with the [CloudEvent spec constraints](https://github.com/cloudevents/spec/blob/v1.0.2/cloudevents/spec.md#source-1) |
+| type | CloudEvent type | string | no if `source` is set, otherwise yes  |
 | kind | Defines the event is either `consumed` or `produced` by the workflow. Default is `consumed` | enum | no |
 | [correlation](#Correlation-Definition) | Define event correlation rules for this event. Only used for consumed events | array | no |
 | dataOnly | If `true` (default value), only the Event payload is accessible to consuming Workflow states. If `false`, both event payload and context attributes should be accessible | boolean | no |