add documentation

Author: anafalcao

Diff for: aws_lambda_powertools/metrics/metrics.py

@@ -47,6 +47,8 @@ def lambda_handler():
         metric namespace
     POWERTOOLS_SERVICE_NAME : str
         service name used for default dimension
+    POWERTOOLS_METRICS_DISABLED: bool
+        Powertools metrics disabled (e.g. `"true", "True", "TRUE"`)
 
     Parameters
     ----------

Diff for: docs/core/metrics.md

@@ -34,12 +34,16 @@ If you're new to Amazon CloudWatch, there are five terminologies you must be awa
 ???+ tip
     All examples shared in this documentation are available within the [project repository](https://github.com/aws-powertools/powertools-lambda-python/tree/develop/examples){target="_blank"}.
 
-Metric has two global settings that will be used across all metrics emitted:
+Metric has three global settings that will be used across all metrics emitted:
 
 | Setting              | Description                                                                     | Environment variable           | Constructor parameter |
 | -------------------- | ------------------------------------------------------------------------------- | ------------------------------ | --------------------- |
 | **Metric namespace** | Logical container where all metrics will be placed e.g. `ServerlessAirline`     | `POWERTOOLS_METRICS_NAMESPACE` | `namespace`           |
 | **Service**          | Optionally, sets **service** metric dimension across all metrics e.g. `payment` | `POWERTOOLS_SERVICE_NAME`      | `service`             |
+| **Disable Powertools Metrics**          | Optionally, disables all Powertools metrics.	 | `POWERTOOLS_METRICS_DISABLED`      | N/A            |
+
+???+ warning
+    `POWERTOOLS_METRICS_DISABLED` will not disable default metrics created by AWS services.
 
 ???+ tip
     Use your application or main service as the metric namespace to easily group all metrics.
@@ -79,7 +83,7 @@ You can create metrics using `add_metric`, and you can create dimensions for all
     CloudWatch EMF supports a max of 100 metrics per batch. Metrics utility will flush all metrics when adding the 100th metric. Subsequent metrics (101th+) will be aggregated into a new EMF object, for your convenience.
 
 ???+ warning "Warning: Do not create metrics or dimensions outside the handler"
-    Metrics or dimensions added in the global scope will only be added during cold start. Disregard if you that's the intended behavior.
+    Metrics or dimensions added in the global scope will only be added during cold start. Disregard if that's the intended behavior.
 
 ### Adding high-resolution metrics
 

Diff for: docs/core/metrics/datadog.md

@@ -23,7 +23,7 @@ stateDiagram-v2
     DatadogExtension --> Datadog: async
 
     state LambdaExtension {
-        DatadogExtension 
+        DatadogExtension
     }
 
 ```
@@ -178,6 +178,10 @@ You can use any of the following environment variables to configure `DatadogMetr
 | -------------------- | -------------------------------------------------------------------------------- | ------------------------------ | --------------------- |
 | **Metric namespace** | Logical container where all metrics will be placed e.g. `ServerlessAirline`      | `POWERTOOLS_METRICS_NAMESPACE` | `namespace`           |
 | **Flush to log**     | Use this when you want to flush metrics to be exported through Datadog Forwarder | `DD_FLUSH_TO_LOG`              | `flush_to_log`        |
+| **Disable Powertools Metrics**          | Optionally, disables all Powertools metrics.	 | `POWERTOOLS_METRICS_DISABLED`      | N/A            |
+
+???+ warning
+    `POWERTOOLS_METRICS_DISABLED` will not disable default metrics created by AWS services.
 
 ## Advanced