Support SNS as a destination

[lezzago]

Issue #, if available:
#91
Description of changes:
Support SNS as a destination

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Merging #348 (558504a) into main (9f2f2cd) will increase coverage by 0.34%.
The diff coverage is 74.39%.

@@             Coverage Diff              @@
##               main     #348      +/-   ##
============================================
+ Coverage     79.63%   79.98%   +0.34%     
- Complexity      209      245      +36     
============================================
  Files           151      156       +5     
  Lines          5342     5490     +148     
  Branches        700      721      +21     
============================================
+ Hits           4254     4391     +137     
+ Misses          717      708       -9     
- Partials        371      391      +20     

Impacted Files	Coverage Δ	Complexity Δ
...ticsearch/alerting/elasticapi/ElasticExtensions.kt	50.90% <33.33%> (-1.02%)	0.00 <0.00> (ø)
...icsearch/alerting/model/destination/Destination.kt	74.59% <44.44%> (-3.39%)	0.00 <0.00> (ø)
...estination/factory/DestinationFactoryProvider.java	57.14% <50.00%> (-17.86%)	3.00 <1.00> (ø)
...endistroforelasticsearch/alerting/MonitorRunner.kt	78.43% <66.66%> (-0.15%)	0.00 <0.00> (ø)
...relasticsearch/alerting/destination/util/Util.java	71.42% <71.42%> (ø)	7.00 <7.00> (?)
...ing/destination/factory/SNSDestinationFactory.java	73.33% <73.33%> (ø)	6.00 <6.00> (?)
...arch/alerting/destination/util/PropertyHelper.java	73.68% <73.68%> (ø)	3.00 <3.00> (?)
...oforelasticsearch/alerting/settings/AWSSettings.kt	76.92% <76.92%> (ø)	0.00 <0.00> (?)
...forelasticsearch/alerting/model/destination/SNS.kt	77.41% <81.25%> (+77.41%)	0.00 <0.00> (ø)
...earch/alerting/destination/message/SNSMessage.java	85.41% <85.41%> (ø)	15.00 <15.00> (?)
... and 16 more

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[qreshi]

This seems a little strange to me. I'm not sure if we should maintain state on using IAM role in the DestinationType enum class.

It looks like this is mostly used for null assertion in the SNS data class. Perhaps you can remove this variable and instead validate if either roleARN or access/secret is set somewhere. It looks like you do something like that in SNSMessage already, that might be sufficient.

And ideally, we should allow the access/secret settings to be changed using the reload API and if we support that then you can have scenarios where:

1. access/secret settings are originally set
2. SNS Destinations are created (allowing roleARN to be null since snsUseIamRole = false)
3. The access/secret settings are removed, checking roleARN on any subsequent SNS Destination but now you have one that's already created with a null roleARN and no access/secret settings so it bypassed this check.

[lezzago]

I need this in case the customer uses the indexDestination API to create the SNS destination and we need some validation for the role arn.
Also I have updated the code such that snsUseIamRole can change whenever the settings are reloaded.

[lezzago]

There are some problems discovered, will reopen PR once they have been resolved

[skkosuri-amzn]

Do we need accessDeclaredMembers? Could you please double check.

[lezzago]

It is required. The AWS SDK uses jackson databind, which needs accessDeclaredMembers.

[kevinduke10]

Would love this merge!!