Refactoring work to support multi-tenancy and multiple storage, database backends (#598)

* Backend infrastructure
* New backend configuration work
* Factor out KV prefixing
* Don't put assets in the manifest cache
* Removed fancy authentication stuff
* Documentation updates

server/storage_backend.ts

@@ -0,0 +1,22 @@
+import { DiskSpacePrimitives } from "../common/spaces/disk_space_primitives.ts";
+import { SpacePrimitives } from "../common/spaces/space_primitives.ts";
+import { path } from "./deps.ts";
+import { S3SpacePrimitives } from "./spaces/s3_space_primitives.ts";
+
+export function determineStorageBackend(folder: string): SpacePrimitives {
+  if (folder === "s3://") {
+    console.info("Using S3 as a storage backend");
+    return new S3SpacePrimitives({
+      accessKey: Deno.env.get("AWS_ACCESS_KEY_ID")!,
+      secretKey: Deno.env.get("AWS_SECRET_ACCESS_KEY")!,
+      endPoint: Deno.env.get("AWS_ENDPOINT")!,
+      region: Deno.env.get("AWS_REGION")!,
+      bucket: Deno.env.get("AWS_BUCKET")!,
+      prefix: folder.slice(5),
+    });
+  } else {
+    folder = path.resolve(Deno.cwd(), folder);
+    console.info(`Using local disk as a storage backend: ${folder}`);
+    return new DiskSpacePrimitives(folder);
+  }
+}