fix(web): do not allow changing product after registering one

[dgdavid]

Problem

Although it is not possible to change a product after registering one, web interface still rendering the Change product action and does not redirect to the root path when users try to navigates to the product selection.

Solution

Check if there is a registration code set for both,

• Do not render the change product action
• Navigates to root path in case the user reach the selection product path.

Testing

• Added a new unit test
• Manually tested by @jreidinger

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Related to

• Product selection stuck after registration #1891
• refactor(web): do not allow unregistering a product #1882

[jreidinger]

manual test works for me as expected.