Don't initialize Event objects when they won't be sent

[st0012]

Fixes #1683

[codecov-commenter]

Codecov Report

Merging #1687 (a63511f) into master (7697af6) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1687   +/-   ##
=======================================
  Coverage   98.55%   98.55%           
=======================================
  Files         136      136           
  Lines        7691     7695    +4     
=======================================
+ Hits         7580     7584    +4     
  Misses        111      111           

Impacted Files	Coverage Δ
sentry-ruby/lib/sentry/client.rb	100.00% <100.00%> (ø)
sentry-ruby/lib/sentry/hub.rb	100.00% <100.00%> (ø)
sentry-ruby/spec/sentry_spec.rb	99.74% <100.00%> (+<0.01%)	⬆️

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[sl0thentr0py]

hmm ideally this check should be done just once in a centralized place, but I can't see a good place for it without changing too many things, so it's fine for now :)

[st0012]

@sl0thentr0py Yeah I agree with you. I think it depends on whether we expect users to initialize events themselves and call capture_event manually.

If we do, then I think the current approach (2 levels of checks) is necessary.
If we don't, we need to prohibit such usages, which should have its own PR.

[sl0thentr0py]

Event.new should be considered as internal api, users shouldn't really use it directly. Only methods on hub or those exposed directly on the top-level Sentry module are our 'contract'.