User Data Export and import (#699)

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/frontend/pulls/699
Co-authored-by: konrad <k@knt.li>
Co-committed-by: konrad <k@knt.li>

src/helpers/downloadBlob.ts

@@ -0,0 +1,7 @@
+export const downloadBlob = (url: string, filename: string) => {
+	const link = document.createElement('a')
+	link.href = url
+	link.setAttribute('download', filename)
+	link.click()
+	window.URL.revokeObjectURL(url)
+}

src/helpers/migrator.ts

@@ -0,0 +1,38 @@
+export interface Migrator {
+	name: string
+	identifier: string
+	isFileMigrator?: boolean
+}
+
+export const getMigratorFromSlug = (slug: string): Migrator => {
+	switch (slug) {
+		case 'wunderlist':
+			return {
+				name: 'Wunderlist',
+				identifier: 'wunderlist',
+			}
+		case 'todoist':
+			return {
+				name: 'Todoist',
+				identifier: 'todoist',
+			}
+		case 'trello':
+			return {
+				name: 'Trello',
+				identifier: 'trello',
+			}
+		case 'microsoft-todo':
+			return {
+				name: 'Microsoft Todo',
+				identifier: 'microsoft-todo',
+			}
+		case 'vikunja-file':
+			return {
+				name: 'Vikunja Export',
+				identifier: 'vikunja-file',
+				isFileMigrator: true,
+			}
+		default:
+			throw Error('Unknown migrator slug ' + slug)
+	}
+}