fix(router): panic sources grouped together

[fracasula]

Description of the change

I was able to replicate the panic mentioned in the Notion ticket and noticed that the comparison with the source ID in each destination was done considering only the first sourceID encountered (i.e. sourceID := destinationJob.JobMetadataArray[0].SourceID) which made the following code fail.

Then I also realized that the sourceID is not really used by SendData so there shouldn't be a bug there. To make it more clear I dropped sourceID altogether.

Notion Link

Notion Link

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added unit tests for the code
• I have made corresponding changes to the documentation

Security

• The code changed/added as part of this pull request won't create any security issues with how the software is being used.

[codecov]

Codecov Report

Merging #1846 (fd2b825) into master (cd32fb7) will increase coverage by 0.04%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master    #1846      +/-   ##
==========================================
+ Coverage   24.26%   24.30%   +0.04%     
==========================================
  Files         122      122              
  Lines       24336    24347      +11     
==========================================
+ Hits         5904     5918      +14     
+ Misses      18088    18085       -3     
  Partials      344      344              

Impacted Files	Coverage Δ
...stomdestinationmanager/customdestinationmanager.go	0.00% <0.00%> (ø)
router/router.go	64.10% <52.94%> (+0.13%)	⬆️
gateway/gateway.go	48.55% <0.00%> (+0.20%)	⬆️
services/debugger/uploader.go	100.00% <0.00%> (+4.00%)	⬆️

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[cisse21]

LGTM

[atzoum]

My only comment is about the pull request's title