Abstract Pipeline Trigger CRUD logic into Services

Problem

Currently, there are no centralized service classes for Ci::Trigger CRUD. It could lead to inconsistent behaviors across different endpoints e.g. RestAPI vs Graphql

Proposal

Abstract the CRUD logic into service classes

Here is my suggestion to refactor these code !128838 (closed)

Auto generated

The following discussion from !125887 (merged) should be addressed:

• @shinya.maeda started a discussion:

  Suggestion: Should we abstract the CRUD logic into service classes? It's currently a bit cumbersome to verify if this endpoint behavior is consistent with the other endpoint behaviors. It's also likely that these independent logic is going to diverge at some points.

  Here is my suggestion to refactor these code !128838 (closed)

  Technically speaking, this refactoring is not a blocker provided that we manually verify the consistency in this MR.