cli: verify embedded examples

[tiborsimko]

Epic

Go through embedded docs (reana-client --help) and verify all its content and provided examples.

Current behaviour

For example, for secrets-add command, we are showing how to add PASSWORD, but this is not a good thing to advocate security wise, and moreover it is not the technique we are using anywhere, so it would be better to show keytab-related example.

$ reana-client secrets-add --help

  Examples:

       $ reana-client secrets-add --env PASSWORD=password

       $ reana-client secrets-add --file ~/.keytab

       $ reana-client secrets-add --env USER=reanauser

                                  --env PASSWORD=password

                                  --file ~/.keytab

Expected behaviour

The same help but with less critical example, such as

  MYSECRET=mysecretvalue

or even better targeted to CERN users:

  CERN_USER=johndoe

so that the output of --help command could be readily used by people wanting to run CERN HTCondor/Slurm scenarios without even having to refer to external documentation.

Note

PASSWORD example is used in a few places:

$ git grep PASSWORD
reana_client/cli/secrets.py:40:         'e.g. PASSWORD=password123')
reana_client/cli/secrets.py:60:    \t $ reana-client secrets-add --env PASSWORD=password \n
reana_client/cli/secrets.py:63:    \t                            --env PASSWORD=password \n
reana_client/cli/secrets.py:109:    \t $ reana-client secrets-delete PASSWORD