feat(config): allow custom admin and sendername for inbucket

[avallete]

What kind of change does this PR introduce?

• Add sender_name and admin_email for inbucket service configuration

What is the current behavior?

Please link any relevant issues here.

What is the new behavior?

Feel free to include screenshots if it includes visual changes.

Additional context

Related #2899

[coveralls]

Pull Request Test Coverage Report for Build 12008936245

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• 7 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.03%) to 59.573%

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Files with Coverage Reduction	New Missed Lines	%
internal/storage/rm/rm.go	2	89.53%
internal/gen/keys/keys.go	5	12.9%

Totals
Change from base Build 12005596418:	-0.03%
Covered Lines:	6397
Relevant Lines:	10738

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💛 - Coveralls