[0.17] Make persistRun transactional

[rh-appservices-perf]

Backport: #2243

Fixes Issue

Fixes #2242

Changes proposed

After deeper investigations it turned out the bug was introduced with #2172 that basically removed the @Transactional annotation around the persistRun method, which is the one invoked by the upload-run async emitter.

My guess is that, given that there is not explicit transaction wrapping that method the roleManager.setRoles(String.join(",", runUpload.roles)); instructions is not visible from the rest of the logic (where the run is persisted) resulting in missing roles at the db level.

Changes:

• Reinstate the @Transactional to the persistRun method
• Force the addRunFromData to produce text/plain

Check List (Check all the applicable boxes)

• My code follows the code style of this project.
• My change requires changes to the documentation.
• I have updated the documentation accordingly.
• All new and existing tests passed.