fix: add missing return after error response in returnDAUsInternal and fix %n format verbs in tests

Bug 1 (coderd/insights.go:85): returnDAUsInternal writes a 500 error
response when GetTemplateInsightsByInterval fails, but does not return.
Execution falls through to write a second 200 OK response with empty
data. Every other error handler in the same file correctly returns after
writing the error response.

Bug 2 (coderd/database/querier_test.go): Four test assertions use %n as
a format verb for an int argument. %n is not a valid Go fmt verb, so on
assertion failure the row index renders as '%!n(int=X)' instead of the
integer. Changed to %d.

coderd/database/querier_test.go

@@ -4421,7 +4421,7 @@ func TestGetUserStatusCounts(t *testing.T) {
 							assert.True(
 								t,
 								rowDate.Equal(expectedDate),
-								"expected date %s, but got %s for row %n",
+								"expected date %s, but got %s for row %d",
 								expectedDate.String(),
 								rowDate.String(),
 								i,
@@ -4594,7 +4594,7 @@ func TestGetUserStatusCounts(t *testing.T) {
 							require.True(
 								t,
 								rowDate.Equal(expectedDate),
-								"expected date %s, but got %s for row %n",
+								"expected date %s, but got %s for row %d",
 								expectedDate.String(),
 								rowDate.String(),
 								i,
@@ -4797,7 +4797,7 @@ func TestGetUserStatusCounts(t *testing.T) {
 					require.True(
 						t,
 						row.Date.In(tc.location).Equal(dbtime.StartOfDay(userCreatedAt).AddDate(0, 0, 1+i)),
-						"expected date %s, but got %s for row %n",
+						"expected date %s, but got %s for row %d",
 						dbtime.StartOfDay(userCreatedAt).AddDate(0, 0, 1+i),
 						row.Date.In(tc.location).String(),
 						i,
@@ -4864,7 +4864,7 @@ func TestGetUserStatusCounts(t *testing.T) {
 					assert.True(
 						t,
 						row.Date.Equal(target),
-						"expected date %s, but got %s for row %n",
+						"expected date %s, but got %s for row %d",
 						target.String(),
 						row.Date.String(),
 						i,

coderd/insights.go

@@ -82,6 +82,7 @@ func (api *API) returnDAUsInternal(rw http.ResponseWriter, r *http.Request, temp
 			Message: "Internal error fetching DAUs.",
 			Detail:  err.Error(),
 		})
+		return
 	}
 
 	resp := codersdk.DAUsResponse{