Add a new API endpoint that will fetch and save Tutorial flows at server boot-time (unless disabled)

[anna-geller]

Feature description

To do:

• add an API endpoint that will fetch blueprints tagged as "Getting Started" and save them into the tutorial namespace at server boot-time
• add a configuration that allows disabling preloading example flows - see example syntax below

kestra:
  tutorial-flows:
    enabled: true # true by default, can be set to false for production; OSS-only

Some extra notes:

• Those flows will be only preloaded in the OSS edition, EE users don't need it
• It's critical for the onboarding tour that those flows already exist in the instance. It's not enough to point to blueprints. The flows need to exist by default in a kestra instance so that new users trying the product for the first time see example workflows even if they skip the onboarding tour New onboarding flow #3567

[anna-geller]

likely no new endpoint is needed, just using this existing endpoint to fetch the Getting Started blueprints and loading them to the tutorial namespace at server boot-time in OSS