🎨 prepare to make the database name configurable

We should not hardcode the database name at different places in
db.Init(). This will allow to make the database path configurable
in a later change, and importantly prevent discrepancies

db/db.go

@@ -4,6 +4,7 @@ import (
 	"database/sql"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"log"
 
 	"git.beisel.it/florian/hostname-service/models"
@@ -17,16 +18,16 @@ import (
 var DB *sql.DB
 
 // Initialize the database and create tables if they don't exist
-func Init() {
+func Init(db string) {
 	var err error
-	DB, err = sql.Open("sqlite3", "hostname-service.db")
+	DB, err = sql.Open("sqlite3", db)
 	if err != nil {
 		log.Fatalf("Error opening database: %v", err)
 	}
 
 	m, err := migrate.New(
 		"file://db/migrations/",
-		"sqlite3://hostname-service.db",
+		fmt.Sprintf("sqlite3://%s", db),
 	)
 
 	if err != nil {