Avoid duplicate tag errors in the backend

[joseAyudarte91]

Some times the backend throws errors when we try to create tags that already exist in different situations:

• Creating/updating stakeholder profiles, when using same tag for Offering/Seeking or Expertise-related contexts.
• Some times the frontend does not provide the backend with the tag ids when submitting them at the time of creating resources, so the backend thinks those are new tags to be created.

In this case, we want the backend to stop throwing errors and use the tags that already exist when needed, making the process transparent for the frontend.