feat: reverse shares (#86)

* add first concept

* add reverse share funcionality to frontend

* allow creator to limit share expiration

* moved reverse share in seperate module

* add table to manage reverse shares

* delete complete share if reverse share was deleted

* optimize function names

* add db migration

* enable reverse share email notifications

* fix config variable descriptions

* fix migration for new installations

frontend/src/utils/fileSize.util.ts

@@ -0,0 +1,23 @@
+export function byteToHumanSizeString(bytes: number) {
+  const sizes = ["B", "KB", "MB", "GB", "TB"];
+  if (bytes == 0) return "0 Byte";
+  const i = parseInt(Math.floor(Math.log(bytes) / Math.log(1024)).toString());
+  return (bytes / Math.pow(1024, i)).toFixed(1).toString() + " " + sizes[i];
+}
+
+export function byteToUnitAndSize(bytes: number) {
+  const units = ["B", "KB", "MB", "GB", "TB"];
+  if (bytes == 0) return { unit: "B", size: 0 };
+  const i = parseInt(Math.floor(Math.log(bytes) / Math.log(1024)).toString());
+
+  return {
+    size: parseFloat((bytes / Math.pow(1024, i)).toFixed(1)),
+    unit: units[i],
+  };
+}
+
+export function unitAndSizeToByte(unit: string, size: number) {
+  const units = ["B", "KB", "MB", "GB", "TB"];
+  const i = units.indexOf(unit);
+  return Math.pow(1024, i) * size;
+}