api-doc examples should provide password as ******

[zmstone]

What happened?

The examples in api-doc contain example passwords which can be confusing for some security researchers.
we should provide all examples as ****** instead.

What did you expect to happen?

****** as password example.

How can we reproduce it (as minimally and precisely as possible)?

No response

Anything else we need to know?

No response

EMQX version

$ ./bin/emqx_ctl broker
# paste output here

OS version

# On Linux:
$ cat /etc/os-release
# paste output here
$ uname -a
# paste output here

# On Windows:
C:\> wmic os get Caption, Version, BuildNumber, OSArchitecture
# paste output here

Log files