Extract message cache into message/ package with model/ types

Move message cache from server/message_cache.go into a dedicated
message/ package with Store interface, SQLite and PostgreSQL
implementations. Extract shared types into model/ package.

message/store_postgres_schema.go

@@ -0,0 +1,90 @@
+package message
+
+import (
+	"database/sql"
+	"fmt"
+)
+
+// Initial PostgreSQL schema
+const (
+	pgCreateTablesQuery = `
+		CREATE TABLE IF NOT EXISTS message (
+			id BIGSERIAL PRIMARY KEY,
+			mid TEXT NOT NULL,
+			sequence_id TEXT NOT NULL,
+			time BIGINT NOT NULL,
+			event TEXT NOT NULL,
+			expires BIGINT NOT NULL,
+			topic TEXT NOT NULL,
+			message TEXT NOT NULL,
+			title TEXT NOT NULL,
+			priority INT NOT NULL,
+			tags TEXT NOT NULL,
+			click TEXT NOT NULL,
+			icon TEXT NOT NULL,
+			actions TEXT NOT NULL,
+			attachment_name TEXT NOT NULL,
+			attachment_type TEXT NOT NULL,
+			attachment_size BIGINT NOT NULL,
+			attachment_expires BIGINT NOT NULL,
+			attachment_url TEXT NOT NULL,
+			attachment_deleted BOOLEAN NOT NULL DEFAULT FALSE,
+			sender TEXT NOT NULL,
+			user_id TEXT NOT NULL,
+			content_type TEXT NOT NULL,
+			encoding TEXT NOT NULL,
+			published BOOLEAN NOT NULL DEFAULT FALSE
+		);
+		CREATE INDEX IF NOT EXISTS idx_message_mid ON message (mid);
+		CREATE INDEX IF NOT EXISTS idx_message_sequence_id ON message (sequence_id);
+		CREATE INDEX IF NOT EXISTS idx_message_time ON message (time);
+		CREATE INDEX IF NOT EXISTS idx_message_topic ON message (topic);
+		CREATE INDEX IF NOT EXISTS idx_message_expires ON message (expires);
+		CREATE INDEX IF NOT EXISTS idx_message_sender ON message (sender);
+		CREATE INDEX IF NOT EXISTS idx_message_user_id ON message (user_id);
+		CREATE INDEX IF NOT EXISTS idx_message_attachment_expires ON message (attachment_expires);
+		CREATE TABLE IF NOT EXISTS message_stats (
+			key TEXT PRIMARY KEY,
+			value BIGINT
+		);
+		INSERT INTO message_stats (key, value) VALUES ('messages', 0);
+		CREATE TABLE IF NOT EXISTS schema_version (
+			store TEXT PRIMARY KEY,
+			version INT NOT NULL
+		);
+	`
+)
+
+// PostgreSQL schema management queries
+const (
+	pgCurrentSchemaVersion     = 14
+	pgInsertSchemaVersion      = `INSERT INTO schema_version (store, version) VALUES ('message', $1)`
+	pgSelectSchemaVersionQuery = `SELECT version FROM schema_version WHERE store = 'message'`
+)
+
+func setupPostgresDB(db *sql.DB) error {
+	var schemaVersion int
+	err := db.QueryRow(pgSelectSchemaVersionQuery).Scan(&schemaVersion)
+	if err != nil {
+		return setupNewPostgresDB(db)
+	}
+	if schemaVersion > pgCurrentSchemaVersion {
+		return fmt.Errorf("unexpected schema version: version %d is higher than current version %d", schemaVersion, pgCurrentSchemaVersion)
+	}
+	return nil
+}
+
+func setupNewPostgresDB(db *sql.DB) error {
+	tx, err := db.Begin()
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback()
+	if _, err := tx.Exec(pgCreateTablesQuery); err != nil {
+		return err
+	}
+	if _, err := tx.Exec(pgInsertSchemaVersion, pgCurrentSchemaVersion); err != nil {
+		return err
+	}
+	return tx.Commit()
+}