fix: evaluate async conditions in the custom bearer token interceptor

[Tlepel]

fix #618

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• [Not applicable] Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: #618

What is the new behavior?

Async conditions are evaluated properly

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[mauriciovigolo]

Great work @Tlepel!

It will be part of milestone 19.10.0.