feat: improve performance

[haveiss]

Background

• The function getActiveGrantsMap retrieves all active grants, resulting in slow performance when a large number of records are returned.
• Some queries are slows due to not having an index

Changes

• refactored to filter existing active grants in the database instead of retrieving all active data and filtering it on the application side.
• add indexes for slow queries

[coveralls]

Pull Request Test Coverage Report for Build 4170570713

• 19 of 23 (82.61%) changed or added relevant lines in 1 file are covered.
• 81 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.02%) to 75.277%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
core/appeal/service.go	19	23	82.61%
<!--	Total:	19	23	82.61%	-->

Files with Coverage Reduction	New Missed Lines	%
core/appeal/service.go	81	81.14%
<!--	Total:	81		-->

Totals
Change from base Build 4111850609:	0.02%
Covered Lines:	7670
Relevant Lines:	10189

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💛 - Coveralls