Config changes

- a source's interval must be greater than 0: a source is turned off with
  enabled, not with a zero interval, so JSCSourcesSource rejects an interval of
  0 or less (its validate is promoted to each source's section);
- max_message_size rejects -1: JSCServerWebSocket rejects a max_message_size
  of -1 (util.ByteSizeNoLimit), as a client could then exhaust the server's
  memory;
- every setting documents what 0 or empty means (zero/none, no limit or a
  default).

internal/config/conf_sections_test.go

@@ -527,3 +527,49 @@ func TestViperValue(t *testing.T) {
 		}
 	}
 }
+
+// max_message_size can't be -1 (no limit), directly or through the whole
+// configuration; 0 (the default) and explicit sizes are accepted.
+func TestWebSocketMaxMessageSizeNoLimit(t *testing.T) {
+	var c JSCServerWebSocket
+	if err := c.SetValue("max_message_size", "-1"); err == nil ||
+		!strings.Contains(err.Error(), "can't be -1") {
+		t.Errorf("SetValue(max_message_size, -1) = %v; want rejected", err)
+	}
+	if c.MaxMessageSize != 0 {
+		t.Errorf("rejected size was stored: %v", c.MaxMessageSize)
+	}
+	for _, text := range []string{"0B", "64KiB"} {
+		if err := c.SetValue("max_message_size", text); err != nil {
+			t.Errorf("SetValue(max_message_size, %s): %v", text, err)
+		}
+	}
+	conf := defaultConfig(t)
+	if err := conf.SetValue("server.websocket.max_message_size", "-1"); err == nil {
+		t.Error("JobSearchConfig.SetValue(server.websocket.max_message_size, -1) succeeded")
+	}
+}
+
+// A source's interval must be greater than 0, through the embedded section's
+// promoted validate; a source is turned off with enabled.
+func TestSourceIntervalMustBePositive(t *testing.T) {
+	conf := defaultConfig(t)
+	for _, key := range []string{
+		"sources.find_a_tender.interval",
+		"sources.fts_mock.interval",
+		"sources.sleeper.interval",
+	} {
+		for _, value := range []string{"0s", "-1m"} {
+			err := conf.SetValue(key, value)
+			if err == nil || !strings.Contains(err.Error(), "greater than 0") {
+				t.Errorf("SetValue(%s, %s) = %v; want rejected", key, value, err)
+			}
+		}
+		if err := conf.SetValue(key, "1m"); err != nil {
+			t.Errorf("SetValue(%s, 1m): %v", key, err)
+		}
+	}
+	if conf.Sources.FindATender.Interval.Minutes() != 1 {
+		t.Errorf("FindATender.Interval = %v; want 1m", conf.Sources.FindATender.Interval)
+	}
+}