Auth Cookie Support (#285)

* Auth cookie support

* Add config option for auth cookie support

* Safe handling of TEGid/auth_id strings

* Fix bad size calculation due to pointer cast

* Expiration timestamp instead of valid bit

* Change setting to "allowed auth methods"

This allows plaintext password auth to be disabled altogether

* PR feedback

sql/migration4.sql

@@ -0,0 +1,19 @@
+/*
+    It is recommended in the SQLite manual to turn off
+    foreign keys when making schema changes that involve them
+*/
+PRAGMA foreign_keys=OFF;
+BEGIN TRANSACTION;
+-- New table to store auth cookies
+CREATE TABLE Auth (
+    AccountID   INTEGER NOT NULL,
+    Cookie      TEXT NOT NULL,
+    Expires     INTEGER DEFAULT 0 NOT NULL,
+    FOREIGN KEY(AccountID) REFERENCES Accounts(AccountID) ON DELETE CASCADE,
+    UNIQUE (AccountID)
+);
+-- Update DB Version
+UPDATE Meta SET Value = 5 WHERE Key = 'DatabaseVersion';
+UPDATE Meta SET Value = strftime('%s', 'now') WHERE Key = 'LastMigration';
+COMMIT;
+PRAGMA foreign_keys=ON;