Store the SmartEdit preview token, include it in all OCC CMS calls, add contracts

[Xymmer]

Dependency on CMSX-7968 and after #493 and #517

Spartacus must store the SmartEdit preview token and include it in all the backend calls to OCC. Some info here: https://wiki.hybris.com/display/CxM/SmartEdit+Support+for+Spartacus

Tobias: I was thinking of passing it as a query param, similar to what we currently do for the accelerator storefront. for example:

• https://localhost:9002/yacceleratorstorefront?site=electronics&cmsTicketId=123456
• http://localhost:4200?cmsTicketId=123456

• receive preview token
• where do we store it -- Should be very similar to language interceptor -- Put it somewhere in ngrx store, use language interceptor as example

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• create http interceptor in occ module, add it to each call should not always be running, should not run on public available site

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Pages/slot/component contracts was added in this ticket

QA:

• In SmartEdit, no console errors
• In SmartEdit, you see the slots you can see the highlights when you point at cms components
• Cannot edit yet

[Xymmer]

talk to wei if unsure how to do this one

[WeizhengSap]

PR: https://github.com/SAP/cloud-commerce-spartacus-storefront/pull/667