chore(medusa): First crud service basic implementation

[adrien2p]

[PERSONAL TEST] Do not merge or review for now :) it is only a draft of my mind and could be a no go depending on discussion

Probably require the migration to typeorm 0.3 to continue and validate this one around a discussion

It is probable that this service will only includes common Read and Delete methods. For the create and update it could include a basic implementation that some services could use as well as the external users. For the services that implement complex create/update they would still keep their own implementation since it is related to specific needs that we don't want to change and probably don't want to make generic since it could break the responsibilities which we want to avoid.

Depends on https://github.com/medusajs/medusa/pull/2007 to improve it

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