fix: Move content into to frontend directory

Doing this BEFORE the merge prevents a lot of merge conflicts.

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

frontend/src/components/common/fields/password-again-field.tsx

@@ -0,0 +1,52 @@
+/*
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import React, { useMemo } from 'react'
+import type { CommonFieldProps } from './fields'
+import { Form } from 'react-bootstrap'
+import { Trans, useTranslation } from 'react-i18next'
+
+interface PasswordAgainFieldProps extends CommonFieldProps {
+  password: string
+}
+
+/**
+ * Renders an input field for typing the new password again when registering.
+ *
+ * @param onChange Hook that is called when the entered retype of the password changes.
+ * @param value The currently entered retype of the password.
+ * @param password The password entered into the password input field.
+ */
+export const PasswordAgainField: React.FC<PasswordAgainFieldProps> = ({ onChange, value, password }) => {
+  const { t } = useTranslation()
+
+  const isInvalid = useMemo(() => {
+    return value !== '' && password !== value
+  }, [password, value])
+
+  const isValid = useMemo(() => {
+    return password !== '' && password === value
+  }, [password, value])
+
+  return (
+    <Form.Group>
+      <Form.Label>
+        <Trans i18nKey='login.register.passwordAgain' />
+      </Form.Label>
+      <Form.Control
+        type='password'
+        size='sm'
+        isInvalid={isInvalid}
+        isValid={isValid}
+        onChange={onChange}
+        placeholder={t('login.register.passwordAgain') ?? undefined}
+        className='bg-dark text-light'
+        autoComplete='new-password'
+        required
+      />
+    </Form.Group>
+  )
+}