fix: avoid insertion key dupls in module_configuration table by ups…

…erting on conflict (#2107)

Fixes #2084

This PR addresses the config side, whereas
#2105 fixed it for secrets.

I confirmed the test fails before this change but passes with it:

```
$ go test ./common/configuration/dal/... -run TestModuleConfiguration
debug:migrate: Applying: 20231103205514_init.sql
debug:migrate: Applied: 20231103205514_init.sql in 134.088875ms
debug:migrate: Applying: 20240704103403_create_module_secrets.sql
debug:migrate: Applied: 20240704103403_create_module_secrets.sql in 5.793958ms
--- FAIL: TestModuleConfiguration (0.30s)
    --- FAIL: TestModuleConfiguration/HandlesConflicts (0.00s)
        dal_test.go:108: Did not expect an error but got:
            duplicate key value violates unique constraint "module_configuration_module_name_key": conflict
FAIL
FAIL	github.com/TBD54566975/ftl/common/configuration/dal	0.760s
FAIL
$ go test ./common/configuration/dal/... -run TestModuleConfiguration
ok  	github.com/TBD54566975/ftl/common/configuration/dal	0.775s
```

common/configuration/dal/dal_test.go

@@ -100,6 +100,13 @@ func TestModuleConfiguration(t *testing.T) {
 			assert.Equal(t, sortedList[i].Name, gotList[i].Name)
 		}
 	})
+
+	t.Run("HandlesConflicts", func(t *testing.T) {
+		err := dal.SetModuleConfiguration(ctx, optional.Some("echo"), "my_config", []byte(`""`))
+		assert.NoError(t, err)
+		err = dal.SetModuleConfiguration(ctx, optional.Some("echo"), "my_config", []byte(`""`))
+		assert.NoError(t, err)
+	})
 }
 
 func TestModuleSecrets(t *testing.T) {

common/configuration/sql/queries.sql

@@ -14,7 +14,8 @@ ORDER BY module, name;
 
 -- name: SetModuleConfiguration :exec
 INSERT INTO module_configuration (module, name, value)
-VALUES ($1, $2, $3);
+VALUES ($1, $2, $3)
+ON CONFLICT (module, name) DO UPDATE SET value = $3;
 
 -- name: UnsetModuleConfiguration :exec
 DELETE FROM module_configuration