refactor: update AS entry handling in API and database to support ASN-only entries. Remove prefix field from AS entry structure and adjust related functions and tests. Enhance OpenAPI specifications and documentation to reflect changes in AS entry representation.

migrations/postgres/000003_as_entry_asn_only.up.sql

@@ -0,0 +1,9 @@
+-- AS-запись: только ASN + community; снимок ревизии может хранить ключи вида as:<asn>.
+ALTER TABLE revision_materialized_prefix
+    ALTER COLUMN prefix TYPE TEXT USING prefix::text;
+
+DELETE FROM module_as_entry WHERE asn IS NULL;
+
+ALTER TABLE module_as_entry DROP CONSTRAINT module_as_entry_asn_or_prefix_chk;
+ALTER TABLE module_as_entry DROP COLUMN prefix;
+ALTER TABLE module_as_entry ALTER COLUMN asn SET NOT NULL;