fix: dedupe owners in upsert/patch asset

[sudo-suhas]

• Dedupe owners list based on ID, UUID and Email before calling the repository layer.
• Dedupe owners list based on ID retrieved from DB using the UUID or Email in the repository layer.
• Using the same transaction that is used to create a user for fetching user by UUID/Email to ensure consistent reads for ongoing transaction.
• While patching an asset, carry over the user's UUID if present.
• Add get-by-email/uuid with-transaction variants to user repository.

Closes #7

[coveralls]

Pull Request Test Coverage Report for Build 4509809853

• 72 of 75 (96.0%) changed or added relevant lines in 4 files are covered.
• 4 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.09%) to 86.237%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/store/postgres/asset_repository.go	16	17	94.12%
internal/store/postgres/user_repository.go	29	31	93.55%

Files with Coverage Reduction	New Missed Lines	%
internal/store/postgres/user_repository.go	4	84.16%

Totals
Change from base Build 4509469872:	0.09%
Covered Lines:	5063
Relevant Lines:	5871

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💛 - Coveralls