feat: convert duration to days and appeal rejection notification

[Chief-Rishab]

• convert duration to days if possible for slack approval notification
• send appeal rejection notification for auto rejected steps, which got auto-rejected at appeal creation time
• include labels from dataset & table when fetching resources (prevent Resource.Details["_metadata"] update from users in UpdateResource) (#372 )

[coveralls]

Pull Request Test Coverage Report for Build 4580552373

• 84 of 128 (65.63%) changed or added relevant lines in 9 files are covered.
• 3 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.2%) to 75.279%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
core/provider/service.go	2	3	66.67%
utils/time.go	12	13	92.31%
plugins/providers/bigquery/provider.go	23	26	88.46%
plugins/providers/bigquery/client.go	27	31	87.1%
plugins/providers/bigquery/model.go	8	20	40.0%
core/appeal/service.go	6	29	20.69%
<!--	Total:	84	128	65.63%	-->

Files with Coverage Reduction	New Missed Lines	%
plugins/providers/bigquery/provider.go	1	80.31%
plugins/providers/bigquery/client.go	2	20.74%
<!--	Total:	3		-->

Totals
Change from base Build 4405106078:	0.2%
Covered Lines:	7951
Relevant Lines:	10562

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💛 - Coveralls