[Woo POS][Local Catalog] Enable storing data for multiple sites at once

[joshheald]

Description

This PR adds the ability to store more than one site's data at a time.

Changes

• Updates all our GRDB entities which currently use a remote ID as their primary key, to include siteID in their primary key.
• Changes full sync to delete only the site being synced, not all sites, before inserting data

Steps to reproduce

1. Launch the app logged in to a WPCom account with multiple POS-eligible sites
2. Observe that your site data synced on login (or was checked and found to be less than 24 hours old)
3. Switch to a different POS site – observe that site's data is synced
4. Switch back to the original site – observe that the data does not need to be synced, because it's already there and less than 24 hrs old.

Screenshots

The purple boxes are site 1, the orange boxes are site 2

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• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce iOS Prototype by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce iOS Prototype
	Build Number	pr16120-43c7bf6
	Version	23.2
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	43c7bf6
	Installation URL	08ai327r8io58

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[jaclync]

LGTM, thanks for figuring out the compound primary keys in GRDB there are some failing test cases in CI that seem related.

[jaclync]

nit: is it worth adding a separate column for the "attribute ID" from the API response, if we ever want to differentiate between local vs. global attributes? Similar question for the variation attribute entity.

[joshheald]

That's a separate task on my list (possibly not in linear yet, I can't remember) but I'm planning to make the schema support both types properly before we finalise it. It's just less urgent than this change.

[jaclync]

nit: any reasons for making this extension internal while the same one in other classes stay private?

[joshheald]

In order to refer to the column names by for the variation's attributes relationship:

public static let attributes = hasMany(PersistedProductVariationAttribute.self,
                                           using: ForeignKey([PersistedProductVariationAttribute.CodingKeys.siteID.stringValue,
                                                              PersistedProductVariationAttribute.CodingKeys.productVariationID.stringValue],
                                                             to: primaryKey))

However, that relationship isn't actually working (it's one of the causes of the failing tests) so when I've fixed it I'll check whether this can go back to private or not.

[joshheald]

Yeah, I actually needed to make the others internal too!