Add default value for cron

[b-per]

Fix for #142

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
src/dbt_jobs_as_code
main.py	294	150	49%	106–109, 115, 142–143, 172–175, 181, 216–300, 371–376, 389–390, 408–409, 413–415, 432–481, 511–555, 586–631, 636–637, 641
src/dbt_jobs_as_code/client
__init__.py	177	58	67%	16, 53–54, 62, 89–104, 119–120, 139–140, 147–157, 170–171, 187–188, 205, 215, 245–247, 289–304, 327, 343–344, 354–366, 369–380, 385–394
src/dbt_jobs_as_code/cloud_yaml_mapping
change_set.py	181	34	81%	25–27, 43, 56, 62–63, 120–121, 159, 171, 193, 197–198, 204–206, 221–224, 256–270, 295–304, 323–345, 381–395
src/dbt_jobs_as_code/importer
__init__.py	27	7	74%	14–15, 22–27
src/dbt_jobs_as_code/loader
load.py	96	1	99%	142
src/dbt_jobs_as_code/schemas
__init__.py	23	2	91%	68, 78
common_types.py	62	10	84%	7–8, 12–13, 29–30, 67–68, 86, 92
config.py	14	3	79%	18, 24–25
job.py	107	2	98%	206, 211
TOTAL	1069	267	75%

Tests	Skipped	Failures	Errors	Time
87	0 💤	0 ❌	0 🔥	11.592s ⏱️