Implement workflow in template composer JAX RS calls

Currently, the template composer in the cms has:

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If however there is a preview configuration it should become

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This means, the very first REST call (./composermode) should return whether there is already a preview configuration or not.

We have different behaviour for when there is and when there is no preview config yet:

1) There is already preview config

• publish button is available
• edit button only does a client side toggle

2) There is not yet a preview config

• publish button is disabled or not visible
• edit button does a REST call: /mountId./edit : This call creates a -preview configuration and REFRESHES the website page

When 'publish' is available a click on it calls

/mountId./publish

This removes the website live confguration and replaces the -preview with ''

After this, 'publish' is again disabled, and a click on 'edit' needs to invoke (2)