Improve the documentation to report the refresh token workflow part

[offtherailz]

Description

Update the documentation due to these changes, improving the chart of https://github.com/geosolutions-it/MapStore2/blame/master/docs/developer-guide/integrations/auth.md with refresh token request to the service.

Note: now they are converted in images. To generate images, restore old markdown and export.

https://github.com/geosolutions-it/MapStore2/blame/master/docs/developer-guide/integrations/auth.md

See this https://github.com/orzih/mkdocs-with-pdf/issues/34

Notice:

Now charts are rendered like this:

### Involved changes to document
- [ ] https://github.com/geosolutions-it/geostore/pull/386#pullrequestreview-2429651712
- [ ] https://github.com/geosolutions-it/geostore/pull/385#pullrequestreview-2417759094

Documentation section involved

• [ ] User Guide
• [x] Developer Guide

Other useful information