feat: separate multiple state transitions

[ndr-brt]

What this PR changes/adds

Avoid the Contract service protocol to do a multiple state transition (REQUESTED and AGREEING).
service -> transition to REQUESTED
manager -> transition to AGREEING

Why it does that

Briefly state why the change was necessary.

Further notes

List other areas of code that have changed but are not necessarily linked to the main feature. This could be method signature changes, package declarations, bugs that were encountered and were fixed inline, etc.

Linked Issue(s)

Closes #2962

Checklist

• added appropriate tests?
• performed checkstyle check locally?
• added/updated copyright headers?
• documented public classes/methods?
• added/updated relevant documentation?
• assigned appropriate label? (exclude from changelog with label no-changelog)
• formatted title correctly? (take a look at the CONTRIBUTING and Etiquette for pull requests for details)