fix(sub): keep the client identity on every subscription link (#6098)

876d55f2 put EMAIL/USERNAME in the same first-link-only bucket as the usage
tokens, so a client attached to several inbounds got its email on whichever
inbound sorted first and bare inbound names on all the rest. With the shipped
default template ({{INBOUND}}-{{EMAIL}}|...) that makes every profile after
the first indistinguishable between clients — the point of the token.

The two are not alike: the usage block repeats identical numbers on every
link, while the identity is what tells one imported profile from another.
Restore identity on all body links and leave usage first-link-only.

Reported again in #6029 and #5659, which asked for the same revert.

internal/sub/remark_vars.go

@@ -481,15 +481,6 @@ var connectionTokens = map[string]bool{
 
 var displayRemoveTokens = mergeTokenSets(usageInfoTokens, connectionTokens)
 
-// firstLinkOnlyBodyTokens are stripped from every subscription-body link after a
-// client's first one: the usage/info tokens plus the per-client EMAIL/USERNAME
-// identity. A client app needs the email once, so repeating it on every link of
-// the same subscription is noise — show it on the first link only, like traffic.
-var firstLinkOnlyBodyTokens = mergeTokenSets(usageInfoTokens, map[string]bool{
-	"EMAIL":    true,
-	"USERNAME": true,
-})
-
 func mergeTokenSets(sets ...map[string]bool) map[string]bool {
 	out := make(map[string]bool)
 	for _, set := range sets {
@@ -560,7 +551,7 @@ func (s *SubService) effectiveTemplate(email string) string {
 		s.usageShown = map[string]bool{}
 	}
 	if s.usageShown[email] {
-		return filterRemarkTemplate(translated, firstLinkOnlyBodyTokens)
+		return filterRemarkTemplate(translated, usageInfoTokens)
 	}
 	s.usageShown[email] = true
 	return translated

internal/sub/remark_vars_test.go

@@ -386,8 +386,8 @@ func TestIdentityTokenBodyVsDisplay(t *testing.T) {
 
 	body := &SubService{remarkTemplate: tmpl, subscriptionBody: true, usageShown: map[string]bool{}}
 	_ = body.genTemplatedRemark(inbound, client, "", "ws") // first link consumes the usage block
-	if second := body.genTemplatedRemark(inbound, client, "", "ws"); strings.Contains(second, "john@x") {
-		t.Fatalf("repeat body link %q must drop the identity token", second)
+	if second := body.genTemplatedRemark(inbound, client, "", "ws"); !strings.Contains(second, "john@x") {
+		t.Fatalf("repeat body link %q must keep the identity token", second)
 	}
 
 	display := &SubService{remarkTemplate: tmpl, subscriptionBody: false}
@@ -624,7 +624,10 @@ func TestUsageOnFirstLinkOnly_SingleBracket(t *testing.T) {
 	}
 }
 
-func TestEmailOnFirstLinkOnly(t *testing.T) {
+// Every link of a subscription carries the client's identity, because that is
+// what tells one imported profile from another in the client app. Only the
+// usage block, which is identical on all of them, is first-link-only (#6098).
+func TestEmailOnEveryLink(t *testing.T) {
 	s := &SubService{
 		remarkTemplate:   "{{INBOUND}} {{EMAIL}}|📊{{TRAFFIC_LEFT}}",
 		subscriptionBody: true,
@@ -640,15 +643,22 @@ func TestEmailOnFirstLinkOnly(t *testing.T) {
 	}
 	client := model.Client{Email: "alice@x"}
 	first := s.genTemplatedRemark(inbound, client, "", "ws")
-	s.usageShown["alice@x"] = true
 	second := s.genTemplatedRemark(inbound, client, "", "ws")
-	if !strings.Contains(first, "alice@x") {
-		t.Fatalf("first link should carry email: %q", first)
+	third := s.genTemplatedRemark(inbound, client, "", "ws")
+	for i, remark := range []string{first, second, third} {
+		if !strings.Contains(remark, "alice@x") {
+			t.Fatalf("link %d must carry the client email: %q", i+1, remark)
+		}
+		if !strings.Contains(remark, "DE") {
+			t.Fatalf("link %d must carry the inbound name: %q", i+1, remark)
+		}
 	}
-	if strings.Contains(second, "alice@x") {
-		t.Fatalf("second link must not carry email: %q", second)
+	if !strings.Contains(first, "📊") {
+		t.Fatalf("first link should carry the usage block: %q", first)
 	}
-	if !strings.Contains(second, "DE") {
-		t.Fatalf("second link should still carry the inbound name: %q", second)
+	for i, remark := range []string{second, third} {
+		if strings.Contains(remark, "📊") {
+			t.Fatalf("repeat link %d must still drop the usage block: %q", i+2, remark)
+		}
 	}
 }