save oauth user_id and link users and accounts

database_migrations/000011_link_users_and_accounts.down.sql

@@ -0,0 +1 @@
+DROP TABLE oauth_users;

database_migrations/000011_link_users_and_accounts.up.sql

@@ -0,0 +1,25 @@
+-- save the oauth user_id to keep track of all known users, and to link to accounts.
+
+CREATE TABLE oauth_users (
+	user_id		TEXT		NOT NULL,
+
+	PRIMARY KEY (user_id)
+);
+
+INSERT INTO oauth_users (
+	user_id
+)
+SELECT
+	DISTINCT id_token_subject
+FROM
+	oauth_tokens;
+
+ALTER TABLE oauth_tokens
+	ADD CONSTRAINT fk_oauth_tokens_oauth_users
+	FOREIGN KEY (id_token_subject)
+	REFERENCES oauth_users (user_id);
+
+ALTER TABLE accounts
+	ADD COLUMN user_id TEXT
+	UNIQUE
+	REFERENCES oauth_users (user_id) NOT NULL;