Update changelog. Add unit test

services/horizon/CHANGELOG.md

@@ -2,6 +2,14 @@
 
 All notable changes to this project will be documented in this
 file. This project adheres to [Semantic Versioning](http://semver.org/).
+## Pending
+
+### Breaking Changes
+
+- `--parallel-job-size` configuration parameter for the `stellar-horizon db reingest` command has been removed.
+  Job size will be automatically determined based on the number of workers (configuration parameter --parallel-workers), distributing
+  the range equally among them. The minimum job size will remain 64 ledgers and the start and end ledger range will be rounded to
+  the nearest checkpoint.([5484](https://github.com/stellar/go/pull/5484))
 
 ## 2.32.0
 

services/horizon/cmd/db_test.go

@@ -45,6 +45,21 @@ func (s *DBCommandsTestSuite) BeforeTest(suiteName string, testName string) {
 	s.rootCmd = NewRootCmd()
 }
 
+func (s *DBCommandsTestSuite) TestInvalidParameterParallelJobSize() {
+	s.rootCmd.SetArgs([]string{
+		"db", "reingest", "range",
+		"--db-url", s.db.DSN,
+		"--network", "testnet",
+		"--parallel-workers", "2",
+		"--parallel-job-size", "10",
+		"--ledgerbackend", "datastore",
+		"--datastore-config", "../internal/ingest/testdata/config.storagebackend.toml",
+		"2",
+		"10"})
+
+	require.Equal(s.T(), "unknown flag: --parallel-job-size", s.rootCmd.Execute().Error())
+}
+
 func (s *DBCommandsTestSuite) TestDbReingestAndFillGapsCmds() {
 	tests := []struct {
 		name          string