fix: add resource_metadata to global_connection datasource schema

The datasource reuses GlobalConnectionResourceModel which now has
ResourceMetadata, but the datasource schema was missing the field.
This caused a schema/model mismatch that silently zeroed state.ID,
resulting in a connections/0/ 404 on every datasource read.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Author: trouze

docs/data-sources/global_connection.md

@@ -25,6 +25,10 @@ data dbtcloud_global_connection my_connection {
 
 - `id` (Number) Connection Identifier
 
+### Optional
+
+- `resource_metadata` (Dynamic) Metadata for tracking resource identity during account migrations. Stored in Terraform state only and not sent to the API.
+
 ### Read-Only
 
 - `adapter_version` (String) Version of the adapter

pkg/framework/objects/global_connection/schema.go

@@ -1172,6 +1172,10 @@ func (r *globalConnectionDataSource) Schema(
 					},
 				},
 			},
+			"resource_metadata": datasource_schema.DynamicAttribute{
+				Optional:    true,
+				Description: "Metadata for tracking resource identity during account migrations. Stored in Terraform state only and not sent to the API.",
+			},
 		},
 	}
 }