Offer the message's own format when replying (#407) (#408)

A reply opened in the format the settings ask for, whatever the message
being answered was written in, and the per-draft switch was buried in
the composer's ⋮ menu. Replying in plain text to a rich text message
throws away the formatting; replying in rich text to a plain-text one
overrides what the sender chose to write in.

When the two disagree the composer now says so above the editor -- "This
message is rich text", with a Switch button and a dismiss -- and the
draft still opens in the format the settings ask for. Switching converts
that draft only and leaves the setting alone; switching from the ⋮ menu
answers the offer too. Forwards get it as well, where the formatting
being passed on is somebody else's.

What counts as rich text is hasHtmlAlternative(), which reads the body
part's own type: `htmlBody` is derived (RFC 8621 4.1.4), so a plain-text
message has one too and its presence proves nothing.

The mock said otherwise -- it returned an empty `htmlBody` for a
plain-text message, where Stalwart 0.16.21 returns the text/plain part
in both lists. Both builders now answer as the server does, so the path
this feature depends on is exercised in development rather than only
against a real mailbox.

Two new strings, translated in all nine catalogs; the buttons reuse the
menu's existing "Switch to plain text" / "Switch to rich text". The
count falling back to English stays at 16 in every language.

Fixes #407

(cherry picked from commit d992442b8194be5e9c48204332c7243d9587b4ca)

web/src/locales/de.ts

@@ -1406,6 +1406,8 @@ export const catalog: Catalog = {
     "Collapse all": "Alle einklappen",
     "Expand all": "Alle ausklappen",
     "Send now instead": "Stattdessen jetzt senden",
+    "This message is rich text": "Diese Nachricht ist formatierter Text",
+    "This message is plain text": "Diese Nachricht ist Nur-Text",
     "Switch to plain text": "Zu Nur-Text wechseln",
     "Switch to rich text": "Zu formatiertem Text wechseln",
     "{used} of {total} used": "{used} von {total} belegt",

web/src/locales/es.ts

@@ -1379,6 +1379,8 @@ export const catalog: Catalog = {
     "Collapse all": "Contraer todo",
     "Expand all": "Expandir todo",
     "Send now instead": "Enviar ahora, sin programar",
+    "This message is rich text": "Este mensaje es texto enriquecido",
+    "This message is plain text": "Este mensaje es texto sin formato",
     "Switch to plain text": "Cambiar a texto sin formato",
     "Switch to rich text": "Cambiar a texto enriquecido",
     "{used} of {total} used": "{used} de {total} usados",

web/src/locales/fr.ts

@@ -1384,6 +1384,8 @@ export const catalog: Catalog = {
     "Collapse all": "Tout réduire",
     "Expand all": "Tout développer",
     "Send now instead": "Envoyer tout de suite",
+    "This message is rich text": "Ce message est en texte enrichi",
+    "This message is plain text": "Ce message est en texte brut",
     "Switch to plain text": "Passer en texte brut",
     "Switch to rich text": "Passer en texte enrichi",
     "{used} of {total} used": "{used} sur {total} utilisés",

web/src/locales/ja.ts

@@ -1387,6 +1387,8 @@ export const catalog: Catalog = {
     "Collapse all": "すべて折りたたむ",
     "Expand all": "すべて展開",
     "Send now instead": "予約をやめて今すぐ送信",
+    "This message is rich text": "このメールはリッチテキストです",
+    "This message is plain text": "このメールはプレーンテキストです",
     "Switch to plain text": "プレーンテキストに切り替え",
     "Switch to rich text": "リッチテキストに切り替え",
     "{used} of {total} used": "{total} 中 {used} を使用",

web/src/locales/nl.ts

@@ -1379,6 +1379,8 @@ export const catalog: Catalog = {
     "Collapse all": "Alles samenvouwen",
     "Expand all": "Alles uitvouwen",
     "Send now instead": "Toch nu verzenden",
+    "This message is rich text": "Dit bericht is opgemaakte tekst",
+    "This message is plain text": "Dit bericht is platte tekst",
     "Switch to plain text": "Overschakelen naar platte tekst",
     "Switch to rich text": "Overschakelen naar opgemaakte tekst",
     "{used} of {total} used": "{used} van {total} gebruikt",

web/src/locales/pt-BR.ts

@@ -1382,6 +1382,8 @@ export const catalog: Catalog = {
     "Collapse all": "Recolher tudo",
     "Expand all": "Expandir tudo",
     "Send now instead": "Enviar agora mesmo",
+    "This message is rich text": "Esta mensagem está em texto formatado",
+    "This message is plain text": "Esta mensagem está em texto simples",
     "Switch to plain text": "Mudar para texto simples",
     "Switch to rich text": "Mudar para texto formatado",
     "{used} of {total} used": "{used} de {total} usados",

web/src/locales/ru.ts

@@ -1381,6 +1381,8 @@ export const catalog: Catalog = {
     "Collapse all": "Свернуть все",
     "Expand all": "Развернуть все",
     "Send now instead": "Отправить сейчас",
+    "This message is rich text": "Это письмо в формате HTML",
+    "This message is plain text": "Это письмо в виде простого текста",
     "Switch to plain text": "Переключиться на обычный текст",
     "Switch to rich text": "Переключиться на форматированный текст",
     "{used} of {total} used": "Использовано {used} из {total}",

web/src/locales/uk.ts

@@ -1375,6 +1375,8 @@ export const catalog: Catalog = {
     "Collapse all": "Згорнути все",
     "Expand all": "Розгорнути все",
     "Send now instead": "Надіслати зараз",
+    "This message is rich text": "Цей лист у форматі HTML",
+    "This message is plain text": "Цей лист у вигляді простого тексту",
     "Switch to plain text": "Перейти на звичайний текст",
     "Switch to rich text": "Перейти на форматований текст",
     "{used} of {total} used": "Використано {used} з {total}",

web/src/locales/zh-Hans.ts

@@ -1386,6 +1386,8 @@ export const catalog: Catalog = {
     "Collapse all": "全部折叠",
     "Expand all": "全部展开",
     "Send now instead": "改为立即发送",
+    "This message is rich text": "这封邮件是富文本",
+    "This message is plain text": "这封邮件是纯文本",
     "Switch to plain text": "切换为纯文本",
     "Switch to rich text": "切换为富文本",
     "{used} of {total} used": "已使用 {used}，共 {total}",