feat: add schema for key rotation (#14662)

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

@@ -0,0 +1,2 @@
+DROP TABLE "crypto_keys";
+DROP TYPE "crypto_key_feature";

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

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+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)
+);
+

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

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+INSERT INTO crypto_keys (feature, sequence, starts_at, secret) VALUES 
+('workspace_apps', 1, now(), 'abc'),
+('oidc_convert', 1, now(), 'def'),
+('tailnet_resume', 1, now(), 'ghi');