fix: sync with master to resolve conflicts

Merge branch 'master' into feat/login-auth

README.md

@@ -47,6 +47,7 @@ To send email user need to create a sender first and then use `Send` method. The
       To              []string // From email field
       Subject         string   // Email subject
       UnsubscribeLink string   // POST, https://support.google.com/mail/answer/81126 -> "Use one-click unsubscribe"
+      InReplyTo       string   // Identifier for email group (category), used for email grouping
       Attachments     []string // Attachments path
       InlineImages    []string // Embedding directly to email body. Autogenerated Content-Id (cid) equals to file name
   }
@@ -60,7 +61,7 @@ See [go docs](https://pkg.go.dev/github.com/go-pkgz/email#Sender.Send) for `Send
 - Custom SMTP client (`smtp.Client` from stdlib) can be set by user with `SMTP` option. In this case it will be used instead of making a new smtp client internally.
 - Logger can be set with `Log` option. It should implement `email.Logger` interface with a single `Logf(format string, args ...interface{})` method. By default, "no logging" internal logger is used. This interface is compatible with the `go-pkgz/lgr` logger.
 - The library has no external dependencies, except for testing. It uses the stdlib `net/smtp` package.
-- SSL/TLS supported with `TLS` option. Pls note: this is not the same as `STARTTLS` (not supported) which is usually on port 587 vs SSL/TLS on port 465.
+- SSL/TLS supported with `TLS` option (usually on port 465) as well as with `STARTTLS` (usually on port 587).
 
 ## limitations
 

email.go

@@ -47,6 +47,7 @@ type Params struct {
 	To              []string // From email field
 	Subject         string   // Email subject
 	UnsubscribeLink string   // POST, https://support.google.com/mail/answer/81126 -> "Use one-click unsubscribe"
+	InReplyTo       string   // Identifier for email group (category), used for email grouping
 	Attachments     []string // Attachments path
 	InlineImages    []string // InlineImages images path
 }
@@ -232,6 +233,10 @@ func (em *Sender) buildMessage(text string, params Params) (message string, err
 		message = addHeader(message, "List-Unsubscribe", "<"+params.UnsubscribeLink+">")
 	}
 
+	if params.InReplyTo != "" {
+		message = addHeader(message, "In-reply-to", "<"+params.InReplyTo+">")
+	}
+
 	withAttachments := len(params.Attachments) > 0
 	withInlineImg := len(params.InlineImages) > 0
 

email_test.go

@@ -313,10 +313,11 @@ func TestEmail_buildMessageWithMIME(t *testing.T) {
 		To:              []string{"to@example.com"},
 		Subject:         "non-ascii symbols: Привет",
 		UnsubscribeLink: "https://example.com/unsubscribe",
+		InReplyTo:       "uuid@example.com",
 	})
 	require.NoError(t, err)
 	assert.Contains(t, msg, "Content-Transfer-Encoding: quoted-printable\nContent-Type: text/html; charset=\"UTF-8\"", msg)
-	assert.Contains(t, msg, "From: from@example.com\nTo: to@example.com\nSubject: =?utf-8?b?bm9uLWFzY2lpIHN5bWJvbHM6INCf0YDQuNCy0LXRgg==?=\nList-Unsubscribe-Post: List-Unsubscribe=One-Click\nList-Unsubscribe: <https://example.com/unsubscribe>\nMIME-version: 1.0", msg)
+	assert.Contains(t, msg, "From: from@example.com\nTo: to@example.com\nSubject: =?utf-8?b?bm9uLWFzY2lpIHN5bWJvbHM6INCf0YDQuNCy0LXRgg==?=\nList-Unsubscribe-Post: List-Unsubscribe=One-Click\nList-Unsubscribe: <https://example.com/unsubscribe>\nIn-reply-to: <uuid@example.com>\nMIME-version: 1.0", msg)
 	assert.Contains(t, msg, "\n\nthis is a test\r\n12345\r\n", msg)
 	assert.Contains(t, msg, "Date: ", msg)
 }