Aggregate follow changes

[dcadenas]

Adds batched messages for follow notifications, new metrics, a way to measure when to aggregate or not and more tests

[coveralls]

Pull Request Test Coverage Report for Build 10674055156

Details

• 374 of 416 (89.9%) changed or added relevant lines in 8 files are covered.
• 8 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.8%) to 59.21%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/domain/follow_change_aggregator.rs	219	221	99.1%
src/domain/follows_differ.rs	5	7	71.43%
src/publisher.rs	29	31	93.55%
src/worker_pool.rs	0	4	0.0%
src/tokio_rate_limiter.rs	11	20	55.0%
src/domain/follow_change_batch.rs	94	104	90.38%
src/account_info.rs	6	19	31.58%

Files with Coverage Reduction	New Missed Lines	%
src/domain/follow_change.rs	1	53.85%
src/domain/follows_differ.rs	2	66.79%
src/worker_pool.rs	5	0.79%

Totals
Change from base Build 10648249586:	0.8%
Covered Lines:	1212
Relevant Lines:	1361

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💛 - Coveralls