<a> tag cannot be used within nav banner

[foxtrot0304]

What happened:
We use the banner to post messages to customers, and sometimes these messages include links using the <a> tag. Currently, the <a> tag cannot be used within the banner, so we would like to fix this issue.

What you expected to happen:
Exclude the <a> tag from sanitization.

How to reproduce it:
Use the <a> tag in the message displayed on the banner.

[foxtrot0304]

The issue below addressed a similar problem.

#2970