Migrate to Typescript

[Akatuoro]

• migrate srv to typescript
• include @cds/typer for generated types -> converted some queries to fluent API
• use ts-jest for tests
• use typescript build task for mta deployment

Todos:

• fiori drafts are not compatible with strict mode used by typescript -> fix in cds needed
• select.one(...).from(...) is typed as PluralType -> currently needs as unknown as ... -> potentially fix types

[cla-assistant[bot]]

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[chgeo]

This is still a fork