feat: Add integration to shiprocket, delhivery, aramex, envia, shippo

[ravibharathi656]

As a part of this PR, I am introducing a new doctype called Shipping Provider to refactor the existing design and introducing the following integration.

• Shiprocket (In Indian context)
• Delhivery (In Indian context)
• Aramex (In Oman context)
• Envia (In Indian context)
• Shippo (In US context)

The existing ones such as letmeship, sendcloud is not affected by this refactoring. Once this is in, will do it as a separate PR.

[barredterra]

Thanks for the PR. Looking forward to integrate these providers.

Regarding the Shipping Provider doctype: when you want to contribute new features, it's a bad idea to change the architecture at the same time. Please stick to the existing architecture. I'm sure there are pros and cons to both. But I think there is not a good reason to change or use two different architectures at the same time.

[Vigneshsekar]

@barredterra ,

As the existing architecture doesn't support having different shipment accounts for different companies within the same site, can we consider migrating LetMeShip and Send Cloud to the new doctype way Shipping Provider?

Also adding 5 more single doctypes for 5 integrations this PR brings may not be good too. What do you suggest?

[Vigneshsekar]

@ravibharathi656 , the currency issue is resolved in another PR. You can remove it, rebase and push it again.

[ravibharathi656]

@barredterra , @Vigneshsekar ,

I used the sync fork feature of GitHub and it closed this PR with a force pushed commits. Let me open a new PR. I will also remove my changes related to the currency as that is taken care in #48 .

Sorry for this inconvenience.

[ravibharathi656]

@barredterra I modified and raised the new PR #50