Add different data providers and improve docs

This adds support for switching between in-memory, local filesystem, s3
or sqlite.

stores/storage.go

@@ -0,0 +1,30 @@
+package stores
+
+import (
+	"excalidraw-complete/core"
+	"excalidraw-complete/stores/aws"
+	"excalidraw-complete/stores/filesystem"
+	"excalidraw-complete/stores/memory"
+	"excalidraw-complete/stores/sqlite"
+	"os"
+)
+
+func GetStore() core.DocumentStore {
+	storageType := os.Getenv("STORAGE_TYPE")
+	var store core.DocumentStore
+
+	switch storageType {
+	case "filesystem":
+		basePath := os.Getenv("LOCAL_STORAGE_PATH")
+		store = filesystem.NewDocumentStore(basePath)
+	case "sqlite":
+		dataSourceName := os.Getenv("DATA_SOURCE_NAME")
+		store = sqlite.NewDocumentStore(dataSourceName)
+	case "s3":
+		bucketName := os.Getenv("S3_BUCKET_NAME")
+		store = aws.NewDocumentStore(bucketName)
+	default:
+		store = memory.NewDocumentStore()
+	}
+	return store
+}