Hide trigger variables in UI by default

Problem to Solve

Currently all variables are shown in UI: http://docs.gitlab.com/ce/ci/triggers/README.html#pass-build-variables-to-a-trigger

This is sometimes problematic, e.g. when you pass individual secrets to the build, which could not be placed in a protected variable and should not be visible to all team members.

It can also be problematic even for some non-protected variables if they are unintentionally passed around in a screenshot/screen sharing.

Solution

• trigger variables is the thing being touched upon here and is either shown or hidden.
• Variable names will still be visible by default
• Variables values will be censored by default with 6 bullet point symbols ••••••
• Variable values are toggle-able with a button
• The button is only available to maintainers
• even if they overwrite an environment variable which is protected, the same functionality still applies as this show/hide functionality is only available to maintainers.
• When a user does not have permission to view those values, the buttons will simply not be there.

Table css measures:

    font-size: 12px;
    line-height: 16px;
    border: 1px solid #dfdfdf;
    padding: 4px 6px;
    width: 50%;

Links / references

http://docs.gitlab.com/ce/ci/triggers/README.html#pass-build-variables-to-a-trigger

Documentation

We should add a new section to https://docs.gitlab.com/ee/ci/variables/ describing how this feature works.