feat(timestamp): Support -/+infinity for Valuer

When converting a timestamp.Timestamp for use in SQL, this now correctly
converts the NegativeInfinity and PositiveInfinity constants into the
corresponding `-infinity` and `infinity` SQL constants.

internal/db/timestamp/scanners.go

@@ -37,10 +37,16 @@ func (ts *Timestamp) Scan(value any) error {
 
 // Scan implements driver.Valuer for protobuf Timestamp.
 func (ts *Timestamp) Value() (driver.Value, error) {
-	if ts == nil {
+	switch {
+	case ts == nil:
 		return nil, nil
+	case ts.AsTime().Equal(NegativeInfinityTS):
+		return "-infinity", nil
+	case ts.AsTime().Equal(PositiveInfinityTS):
+		return "infinity", nil
+	default:
+		return ts.Timestamp.AsTime(), nil
 	}
-	return ts.Timestamp.AsTime(), nil
 }
 
 // GormDataType gorm common data type (required)

internal/db/timestamp/scanners_test.go

@@ -33,6 +33,18 @@ func Test_TimestampValue(t *testing.T) {
 		require.NoError(t, err)
 		assert.Equal(t, v, utcDate(10000, 1, 1))
 	})
+	t.Run("negativeInfinity", func(t *testing.T) {
+		ts := New(NegativeInfinityTS)
+		v, err := ts.Value()
+		require.NoError(t, err)
+		assert.Equal(t, v, "-infinity")
+	})
+	t.Run("positiveInfinity", func(t *testing.T) {
+		ts := New(PositiveInfinityTS)
+		v, err := ts.Value()
+		require.NoError(t, err)
+		assert.Equal(t, v, "infinity")
+	})
 }
 
 func Test_TimestampScan(t *testing.T) {
@@ -65,6 +77,20 @@ func Test_TimestampScan(t *testing.T) {
 		err := ts.Scan(v)
 		require.Nil(err)
 	})
+	t.Run("negativeInfinity", func(t *testing.T) {
+		v := "-infinity"
+		ts := Timestamp{}
+		err := ts.Scan(v)
+		require.NoError(err)
+		assert.Equal(ts.AsTime(), NegativeInfinityTS)
+	})
+	t.Run("positiveInfinity", func(t *testing.T) {
+		v := "infinity"
+		ts := Timestamp{}
+		err := ts.Scan(v)
+		require.NoError(err)
+		assert.Equal(ts.AsTime(), PositiveInfinityTS)
+	})
 }
 
 const maxValidSeconds = 253402300800