Calculate an ETag for an entity. When the entity is a specific set of data it will be fingerprinted as a "strong" tag, otherwise if it is just file information, it will be calculated as a weak tag.

import { calculate } from "https://deno.land/std@0.223.0/http/etag.ts";
import { assert } from "https://deno.land/std@0.223.0/testing/asserts.ts"

const body = "hello deno!";

const etag = await calculate(body);
assert(etag);

const res = new Response(body, { headers: { etag } });