Move more docs to docs folder (#3801)

docs/metrics/customizing-the-sdk/README.md

@@ -446,8 +446,8 @@ The snippet below shows configuring the `Resource` associated with the provider.
 
 ```csharp
 using OpenTelemetry;
-using OpenTelemetry.Resources;
 using OpenTelemetry.Metrics;
+using OpenTelemetry.Resources;
 
 using var meterProvider = Sdk.CreateMeterProviderBuilder()
     .ConfigureResource(r => r.AddService("MyServiceName"))

docs/trace/customizing-the-sdk/README.md

@@ -199,11 +199,63 @@ logging, by supporting `Activity` and `LogRecord` respectively.*
 
 ### Resource
 
-// TODO
+[Resource](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/resource/sdk.md)
+is the immutable representation of the entity producing the telemetry. If no
+`Resource` is explicitly configured, the
+[default](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/resource/semantic_conventions/README.md#semantic-attributes-with-sdk-provided-default-value)
+resource is used to indicate the
+[Service](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/resource/semantic_conventions/README.md#service).
+The `ConfigureResource` method on `TracerProviderBuilder` can be used to
+configure the resource on the provider. When the provider is built, it
+automatically builds the final `Resource` from the configured `ResourceBuilder`.
+There can only be a single `Resource` associated with a
+provider. It is not possible to change the resource builder *after* the provider
+is built, by calling the `Build()` method on the `TracerProviderBuilder`.
+`ResourceBuilder` offers various methods to construct resource comprising of
+multiple attributes from various sources.
+
+The snippet below shows configuring the `Resource` associated with the provider.
+
+```csharp
+using OpenTelemetry;
+using OpenTelemetry.Resources;
+using OpenTelemetry.Trace;
+
+using var tracerProvider = Sdk.CreateTracerProviderBuilder()
+    .ConfigureResource(r => r.AddService("MyServiceName"))
+    .Build();
+```
+
+It is also possible to configure the `Resource` by using following
+environmental variables:
+
+| Environment variable       | Description                                        |
+| -------------------------- | -------------------------------------------------- |
+| `OTEL_RESOURCE_ATTRIBUTES` | Key-value pairs to be used as resource attributes. See the [Resource SDK specification](https://github.com/open-telemetry/opentelemetry-specification/blob/v1.5.0/specification/resource/sdk.md#specifying-resource-information-via-an-environment-variable) for more details. |
+| `OTEL_SERVICE_NAME`        | Sets the value of the `service.name` resource attribute. If `service.name` is also provided in `OTEL_RESOURCE_ATTRIBUTES`, then `OTEL_SERVICE_NAME` takes precedence. |
 
 ### Sampler
 
-// TODO
+[Samplers](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/sdk.md#sampler)
+are used to control the noise and overhead introduced by OpenTelemetry by
+reducing the number of samples of traces collected and sent to the processors.
+If no sampler is explicitly configured, the default is to use
+`ParentBased(root=AlwaysOn)`. `SetSampler` method on `TracerProviderBuilder` can
+be used to set sampler. Only one sampler can be associated with a provider. If
+multiple `SetSampler` is called, the last one wins. Also, it is not possible to
+change the sampler *after* the provider is built, by calling the `Build()`
+method on the `TracerProviderBuilder`.
+
+The snippet below shows configuring a custom sampler to the provider.
+
+```csharp
+using OpenTelemetry;
+using OpenTelemetry.Trace;
+
+using var tracerProvider = Sdk.CreateTracerProviderBuilder()
+    .SetSampler(new TraceIdRatioBasedSampler(0.25))
+    .Build();
+```
 
 ## Context Propagation
 

src/OpenTelemetry.Exporter.Console/ConsoleMetricExporter.cs

@@ -97,15 +97,14 @@ namespace OpenTelemetry.Exporter
                         var bucketsBuilder = new StringBuilder();
                         var sum = metricPoint.GetHistogramSum();
                         var count = metricPoint.GetHistogramCount();
+                        bucketsBuilder.Append($"Sum: {sum} Count: {count} ");
                         if (metricPoint.HasMinMax())
                         {
-                            bucketsBuilder.Append($"Sum: {sum} Count: {count} Min: {metricPoint.GetHistogramMin()} Max: {metricPoint.GetHistogramMax()} \n");
-                        }
-                        else
-                        {
-                            bucketsBuilder.Append($"Sum: {sum} Count: {count} \n");
+                            bucketsBuilder.Append($"Min: {metricPoint.GetHistogramMin()} Max: {metricPoint.GetHistogramMax()} ");
                         }
 
+                        bucketsBuilder.AppendLine();
+
                         bool isFirstIteration = true;
                         double previousExplicitBound = default;
                         foreach (var histogramMeasurement in metricPoint.GetHistogramBuckets())