[-] only create time partitions if needed

[0xgouda]

• Check if the needed time partition already exists before creating new partitions in postgres sink

TODO:

• Add tests
• Ensure a migration exists for the changes

Closes #1126

[coveralls]

Pull Request Test Coverage Report for Build 21290387143

Details

• 17 of 23 (73.91%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.01%) to 75.31%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/sinks/postgres.go	17	23	73.91%

Totals
Change from base Build 21245085454:	0.01%
Covered Lines:	4014
Relevant Lines:	5330

---

💛 - Coveralls

[pashagolub]

Perfect!