Improvement: Update Etsy API to v3

[icemansparks]

Since etsys API v2 will be discontinued and stop working by the end of the year as stated in the etsy documentation ( https://www.etsy.com/developers/documentation/getting_started/edd#section_update_your_app ), it would be wise to update the client to use etsys new v3 API - which is similar but not exactly the same.

Details can be found here: https://developers.etsy.com/documentation/

Great job here btw! It's nice to see an updated etsy node client.

[creharmony]

🧑‍💼 I start to work on it because there is a date for end of v2..

I'll put down here some dev remarks during implementation.

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v2 findAllShops (no mandatory arg) => v3 findShops (shop_name required)

• etsy/open-api#420

v2 getShop (shop name) => v3 getShop (shopId required) v2 findAllShopSections (shop name) => v3 getShopSections (shopId required) v2 findAllShopListingsActive (shop name) => v3 findAllActiveListingsByShop (shopId required)

v2 getListing => v3 getListing doc

• ⚠️ inventory and variations are no more supported in supported includes: [shipping, images, shop, user, translations]
• includes related ticket: etsy/open-api#236 (improvement)
• variations values translations related ticket: etsy/open-api#431 (bug)

v2 getVariationImages => v3 getListingVariationImages (adding shopId) v2 findAllListingImages => v3 getListingImages v2 getInventory => 🔴 v3 getListingInventory - not migrated for now : rely now on strong auth oauth2

v2 getAttributes => v3 getListingProperty (adding shopId) v2 getProduct => 🔴 v3 getListingProduct - not migrated for now : rely now on strong auth oauth2 v2 findAllListingShippingProfileEntries => 🔴 v3 no equivalent

• suggest oauth2 cases tools ✔️ (cf related PR)

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• ✔️ anticipate v2 client cleanup : #41