feat: add schema for key rotation (#14662)

coderd/database/migrations/000251_crypto_keys.up.sql

@@ -0,0 +1,16 @@
+CREATE TYPE crypto_key_feature AS ENUM (
+    'workspace_apps',
+    'oidc_convert',
+    'tailnet_resume'
+);
+
+CREATE TABLE crypto_keys (
+    feature crypto_key_feature NOT NULL,
+    sequence integer NOT NULL,
+    secret text NULL,
+    secret_key_id text NULL REFERENCES dbcrypt_keys(active_key_digest),
+    starts_at timestamptz NOT NULL,
+    deletes_at timestamptz NULL,
+    PRIMARY KEY (feature, sequence)
+);
+