feat: Hide secrets on api and channels

server/internal/api/channels.go

@@ -34,7 +34,14 @@ func listChannels(c *gin.Context) {
 		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
 		return
 	}
-	c.JSON(http.StatusOK, channels)
+	// Redacted here rather than in the service: the dispatchers read the same
+	// documents and need the real credentials, so the masking belongs to the
+	// boundary that hands them to a client.
+	out := make([]models.NotificationChannel, 0, len(channels))
+	for _, ch := range channels {
+		out = append(out, ch.Redacted())
+	}
+	c.JSON(http.StatusOK, out)
 }
 
 // createChannel godoc
@@ -69,7 +76,7 @@ func createChannel(c *gin.Context) {
 		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
 		return
 	}
-	c.JSON(http.StatusCreated, created)
+	c.JSON(http.StatusCreated, created.Redacted())
 }
 
 // updateChannel godoc