Set Default Sequencing Object/Genome Assembly to null when deleted

[deepsidhu85]

Description of changes

What did you change in this pull request? Provide a description of files changed, user interactions changed, etc. Include how to test your changes.

Fixed bug with default sequencing object and default genome assembly not being set to NULL when they are removed from a sample. Moved the setting of the default sequencing object and default genome assembly to SampleService and GenomeAssemblyService respectively

Related issue

Link to the GitHub issue this pull request addresses using the #issuenum format. If it completes an issue, use Fixes #issuenum to automatically close the issue.

To Test:

1. On development branch, add a project and add a sample to the project
2. Launch the sample details viewer and click the files tab
3. Upload 2 paired end files to the sample
4. Set the second pair to be the default sequencing object for the sample
5. Check in the mysql console to make sure it was set as the default sequencing object for the sample
6. Delete the first pair and verify in the mysql console that the default is still set
7. Delete the remaining pair and verify in the mysql console that the default sequencing object is still set even though it was deleted from the sample.
8. Repeat for genome assemblies

Fix:

1. On this branch, add a project and add a sample to the project
2. Launch the sample details viewer and click the files tab
3. Upload 2 paired end files to the sample
4. Set the second pair to be the default sequencing object for the sample
5. Check in the mysql console to make sure it was set as the default sequencing object for the sample
6. Delete the first pair and verify in the mysql console that the default is still set
7. Delete the remaining pair and verify in the mysql console that the default sequencing object is not set to NULL
8. Repeat for genome assemblies

Checklist

Things for the developer to confirm they've done before the PR should be accepted:

• CHANGELOG.md (and UPGRADING.md if necessary) updated with information for new change.
• Tests added (or description of how to test) for any new features.
  * [ ] User documentation updated for UI or technical changes.

[ericenns]

Looks good to me! Thanks again for fixing this is short order