Refactored data sources service for improved structure and asynchronicity

[codecov[bot]]

Codecov Report

Attention: 205 lines in your changes are missing coverage. Please review.

Comparison is base (434003f) 68.25% compared to head (1125eab) 68.24%. Report is 66 commits behind head on project-orion.

Files	Patch %	Lines
app/services/data-sources-service.js	52.21%	54 Missing :warning:
app/controllers/techniques-controller.js	59.34%	37 Missing :warning:
app/controllers/data-sources-controller.js	63.41%	30 Missing :warning:
app/controllers/campaigns-controller.js	64.55%	28 Missing :warning:
app/repository/references-repository.js	81.98%	20 Missing :warning:
app/repository/user-accounts-repository.js	0.00%	14 Missing :warning:
app/services/techniques-service.js	85.18%	8 Missing :warning:
app/repository/_base.repository.js	64.70%	6 Missing :warning:
app/services/references-service.js	84.00%	4 Missing :warning:
app/services/collection-bundles-service.js	83.33%	3 Missing :warning:
... and 1 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## project-orion #337 +/- ## ================================================= - Coverage 68.25% 68.24% -0.01% ================================================= Files 145 146 +1 Lines 15997 15737 -260 Branches 1936 1887 -49 ================================================= - Hits 10918 10740 -178 + Misses 5071 4989 -82 Partials 8 8 ```

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[sonarcloud[bot]]

Quality Gate failed

Failed conditions

7.0% Duplication on New Code (required ≤ 3%)

See analysis details on SonarCloud