Add Authorized users to API by using username

[marla-singer]

Closes #3365

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• Alternative solutions were compared/discussed before writing code
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Reviewed by: @username1

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[matleppa]

Functionality as expected.
However, should we make a little fix in order to make user experience better?

Correction to title:
Add authorized users --> Add new authorized user

Between title and input field a guidance text:
"Give either username or email address"

[marla-singer]

Correction to title:
Add authorized users --> Add new authorized user

Don't agree, "new" is redundant

Between title and input field a guidance text:
"Give either username or email address"

Will do it

[matleppa]

OK.

Add authorized users
-->
Add authorized user

Because users are added one at a time.

[marla-singer]

@matleppa Actual, the original text is in single number (button). Or did you mean the title?

[anarva]

Changes are fine.

[matleppa]

The title, yes. Now it seems to be fine.