feat: move step-ca into a plugin (C4)

plugins/step-ca/migrations/postgres/0001_create_certs.sql

@@ -0,0 +1,16 @@
+-- step-ca 0001: create_certs
+-- Generated by termix-plugin migrations. Review before committing.
+
+CREATE TABLE IF NOT EXISTS "p_step_ca_certs" (
+  "id" serial PRIMARY KEY,
+  "user_id" varchar(255) NOT NULL,
+  "host_id" integer NOT NULL,
+  "ssh_cert" text NOT NULL,
+  "private_key" text NOT NULL,
+  "email" text,
+  "created_at" text NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  "expires_at" varchar(255) NOT NULL,
+  FOREIGN KEY ("user_id") REFERENCES "users" ("id") ON DELETE CASCADE,
+  FOREIGN KEY ("host_id") REFERENCES "ssh_data" ("id") ON DELETE CASCADE
+);
+CREATE UNIQUE INDEX IF NOT EXISTS "idx_step_ca_certs_user_host" ON "p_step_ca_certs" ("user_id", "host_id");