Update integration resource docs for Datadog tags (#277)

The tags attribute for `cloudamqp_integration_log` and `cloudamqp_integration_metric` offer the ability to add tags- useful for cases like USM with Datadog.

Requirement for tags using Datadog, must start with a letter.
https://docs.datadoghq.com/getting_started/tagging/#define-tags

---------

Co-authored-by: Tobias Brodén <tobias@84codes.com>

Author: insanedefaults

docs/resources/integration_log.md

@@ -88,7 +88,7 @@ resource "cloudamqp_integration_log" "datadog" {
   name = "datadog"
   region = var.datadog_region
   api_key = var.datadog_api_key
-  tags = var.datadog_tags
+  tags = "env=prod,region=us1,version=v1.0"
 }
 ```
 
@@ -289,7 +289,10 @@ The following arguments are supported:
 * `access_key_id`     - (Optional/Sensitive) AWS access key identifier.
 * `secret_access_key` - (Optional/Sensitive) AWS secret access key.
 * `api_key`           - (Optional/Sensitive) The API key.
-* `tags`              - (Optional) Tag the integration, e.g. env=prod,region=europe.
+* `tags`              - (Optional) Tags. e.g. `env=prod,region=europe`.
+
+***Note: If tags are used with Datadog. The value part (prod, europe, ...) must start with a letter, read more about tags format in the [Datadog documentation](https://docs.datadoghq.com/getting_started/tagging/#define-tags)***
+
 * `credentials`       - (Optional/Sensitive) Google Service Account private key credentials.
 * `project_id`        - (Optional/Computed) The project identifier.
 * `private_key`       - (Optional/Computed/Sensitive) The private access key.

docs/resources/integration_metric.md

@@ -78,13 +78,15 @@ resource "cloudamqp_integration_metric" "datadog" {
   name = "datadog"
   api_key = var.datadog_api_key
   region = var.datadog_region
+  tags = "env=prod,region=us1,version=v1.0"
 }
 
 resource "cloudamqp_integration_metric" "datadog_v2" {
   instance_id = cloudamqp_instance.instance.id
   name = "datadog_v2"
   api_key = var.datadog_api_key
   region = var.datadog_region
+  tags = "env=prod,region=us1,version=v1.0"
 }
 ```
 
@@ -237,6 +239,9 @@ The following arguments are supported:
 * `private_key`       - (Optional/Computed) The private access key.
 * `client_email`      - (Optional/Computed) The client email registered for the integration service.
 * `tags`              - (Optional) Tags. e.g. `env=prod,region=europe`.
+
+***Note: If tags are used with Datadog. The value part (prod, europe, ...) must start with a letter, read more about tags format in the [Datadog documentation](https://docs.datadoghq.com/getting_started/tagging/#define-tags)***
+
 * `queue_allowlist`   - (Optional) Allowlist queues using regular expression. Leave empty to include all queues.
 * `vhost_allowlist`   - (Optional) Allowlist vhost using regular expression. Leave empty to include all vhosts.
 * `queue_whitelist`   - **Deprecated** Use queue_allowlist instead