Refactor message validation

[eytan-avisror]

Adds to #54

This PR refactors message validation so that it's more accurate and no longer spins up goroutines before the message is validated.
It also removes some redundant functions

[codecov]

Codecov Report

Merging #55 into master will decrease coverage by 0.55%.
The diff coverage is 64.64%.

@@            Coverage Diff             @@
##           master      #55      +/-   ##
==========================================
- Coverage   72.78%   72.23%   -0.56%     
==========================================
  Files          12       12              
  Lines        1018      987      -31     
==========================================
- Hits          741      713      -28     
  Misses        212      212              
+ Partials       65       62       -3     

Impacted Files	Coverage Δ
pkg/service/lifecycle.go	100.00% <ø> (+38.46%)	⬆️
pkg/service/server.go	61.35% <49.09%> (-0.99%)	⬇️
pkg/service/manager.go	71.17% <78.12%> (-10.65%)	⬇️
pkg/service/elb.go	100.00% <100.00%> (ø)
pkg/service/elbv2.go	100.00% <100.00%> (ø)
pkg/service/events.go	82.35% <100.00%> (+3.78%)	⬆️
pkg/service/sqs.go	72.72% <100.00%> (+1.29%)	⬆️

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