Bug 1821243 - Do not require content and template if id is present in message schema r=omc-reviewers,aminomancer

The schema still imposes the following restrictions:

- Having "template" present makes "content" and "id" required.
- Having "content" present makes "template" and "id" required.

Template and content are dependent on eachother because we do not know how to
interpret content without a template and we a template with no content to
interpret is useless.

If we have a template and content, then we also need an ID for the message
because we cannot reference the message content except by its ID.

Differential Revision: https://phabricator.services.mozilla.com/D172458

browser/components/newtab/content-src/asrouter/schemas/BackgroundTaskMessagingExperiment.schema.json

@@ -216,10 +216,6 @@
       },
       "additionalProperties": true,
       "dependentRequired": {
-        "id": [
-          "content",
-          "template"
-        ],
         "content": [
           "id",
           "template"

browser/components/newtab/content-src/asrouter/schemas/FxMSCommon.schema.json

@@ -103,7 +103,6 @@
       },
       "additionalProperties": true,
       "dependentRequired": {
-        "id": ["content", "template"],
         "content": ["id", "template"],
         "template": ["id", "content"]
       }

browser/components/newtab/content-src/asrouter/schemas/MessagingExperiment.schema.json

@@ -1370,10 +1370,6 @@
       },
       "additionalProperties": true,
       "dependentRequired": {
-        "id": [
-          "content",
-          "template"
-        ],
         "content": [
           "id",
           "template"