Add drop_schema_named macro (#8868)

* add drop_schema_named

* give drop_schema_named a default

.changes/unreleased/Features-20231017-143620.yaml

@@ -0,0 +1,6 @@
+kind: Features
+body: Add drop_schema_named macro
+time: 2023-10-17T14:36:20.612289-07:00
+custom:
+  Author: colin-rogers-dbt
+  Issue: "8025"

core/dbt/include/global_project/macros/relations/schema.sql

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+{% macro drop_schema_named(schema_name) %}
+    {{ return(adapter.dispatch('drop_schema_named', 'dbt') (schema_name)) }}
+{% endmacro %}
+
+{% macro default__drop_schema_named(schema_name) %}
+  {% set schema_relation = api.Relation.create(schema=schema_name) %}
+  {{ adapter.drop_schema(schema_relation) }}
+{% endmacro %}

tests/adapter/dbt/tests/adapter/relations/test_dropping_schema_named.py

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+import pytest
+
+from dbt.tests.util import run_dbt, get_connection
+
+
+class BaseDropSchemaNamed:
+    @pytest.fixture(scope="class")
+    def models(self):
+        return {
+            "model_a.sql": "select 1 as id",
+        }
+
+    def test_dropped_schema_named_drops_expected_schema(self, project):
+
+        results = run_dbt(["run"])
+        assert len(results) == 1
+
+        run_dbt(
+            [
+                "run-operation",
+                "drop_schema_named",
+                "--args",
+                f"{{schema_name: {project.test_schema} }}",
+            ]
+        )
+
+        adapter = project.adapter
+        with get_connection(adapter):
+            schemas = adapter.list_schemas(project.database)
+
+        assert project.test_schema not in schemas
+
+
+class TestDropSchemaNamed(BaseDropSchemaNamed):
+    pass