[Telemetry] Full schema definition

.telemetryrc.json

@@ -2,15 +2,6 @@
   {
     "output": "src/plugins/telemetry/schema/oss_plugins.json",
     "root": "src/plugins/",
-    "exclude": [
-      "src/plugins/kibana_react/",
-      "src/plugins/testbed/",
-      "src/plugins/kibana_utils/"
-    ]
-  },
-  {
-    "output": "src/plugins/telemetry/schema/legacy_plugins.json",
-    "root": "src/legacy/server/",
     "exclude": []
   }
 ]

src/plugins/telemetry/schema/README.md

@@ -0,0 +1,17 @@
+# Telemetry Schemas
+
+This list of `.json` files describes the format of the payloads sent to the Remote Telemetry Service. All the files should follow the schema convention as defined in the `usage_collection` plugin and `@kbn/telemetry-tools`.
+
+There are currently 2 files:
+
+- `oss_root.json`: Defines the schema for the payload from the root keys.    
+  Manually maintained for now because the frequency it changes should be pretty low.
+- `oss_plugins.json`: The schema for the content that will be nested in `stack_stats.kibana.plugins`.    
+  It is automatically generated by `@kbn/telemetry-tools` based on the `schema` property provided by all the registered Usage Collectors via the `usageCollection.makeUsageCollector` API.    
+  More details in the [Schema field](../../usage_collection/README.md#schema-field) chapter in the UsageCollection's docs.
+
+NOTE: Despite its similarities to ES mappings, the intention of these files is not to define any index mappings. They should be considered as a tool to understand the format of the payload that will be sent when reporting telemetry to the Remote Service.
+
+## Testing
+
+Functional tests are defined at `test/api_integration/apis/telemetry/telemetry_local.ts`. They merge both files, and validates the actual output of the telemetry endpoint against the final schema.