#8465 Improving API and preventing issues from geostore

[offtherailz]

Description

This PR makes easier to configure the URL. moreover it adds some arguments to prevent this issue on geostore:

geosolutions-it/geostore#311

Waiting for a solution of it

Please check if the PR fulfills these requirements

• The commit message follows our guidelines: https://github.com/geosolutions-it/MapStore2/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x", remove the others)

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

Issue

#8465

What is the current behavior?

• Developers can not easely define the URL of mapstore. (need to use the base URL).
• randomly backend has an issue that doens't allow to start the backend

What is the new behavior?

• The developers can now define MAPSTORE_BACKEND_URL=https://dev-mapstore.geosolutionsgroup.com/mapstore to run on dev

Breaking change

Does this PR introduce a breaking change? (check one with "x", remove the other)

• Yes, and I documented them in migration notes
• No

Other useful information