Refactor es storage

[pavolloffay]

Resolves #1017, #1018 (comment)

• use dependency link from dbmodel package
• move service struct to dbmodel
• rename maxLookBack to maxSpanAge

Signed-off-by: Pavol Loffay ploffay@redhat.com

[codecov]

Codecov Report

Merging #1111 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #1111   +/-   ##
======================================
  Coverage     100%    100%           
======================================
  Files         141     142    +1     
  Lines        6723    6743   +20     
======================================
+ Hits         6723    6743   +20

Impacted Files	Coverage Δ
plugin/storage/es/dependencystore/storage.go	100% <100%> (ø)	⬆️
...in/storage/es/dependencystore/dbmodel/converter.go	100% <100%> (ø)
plugin/storage/es/spanstore/reader.go	100% <100%> (ø)	⬆️
plugin/storage/es/spanstore/writer.go	100% <100%> (ø)	⬆️
plugin/storage/es/factory.go	100% <100%> (ø)	⬆️
plugin/storage/es/spanstore/service_operation.go	100% <100%> (ø)	⬆️

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[pavolloffay]

@jpkrohling would you like to have a look?

[jpkrohling]

LGTM, but I have a stupid question first: can't we have a single DependencyLink? Perhaps we could avoid all this conversion between DB and Model objects...

[pavolloffay]

We have agreed to have a separate db model classes for each storage. It's easier to maintain. E.g. UI model can change without breaking the storage.