UX/Documentation improvement for Valid and Invalid Identifiers inputs

[typecastcloud]

Description

As company admin who is being onboarded,
I want clear guidance (hints, documentation, examples) of what content is expected for identifiers,
so that I don't input the wrong value.

Acceptance Criteria

• Existing hints/descriptions are reviewed
• Clear valid examples are given for (all) identifiers - at least worldwide, germany, european identifiers

Additional Information

[saadanzari]

@typecastcloud pls create sig-release ticket for this.