Add several messages and services

[guenoledc]

Hello,

I want first to thank you for the lib.
I needed the addition of the CAMT.003, 4, 5 and 6 for a project and took the liberty to start from your lib.

Therefore I want to pull back to you the work, in case it suit you.

Changes

• Addition of the CAMT.003, 004, 005, 006 but with limited implementation to focus on the requirements I needed
• Addition of few unit testing following your model
• Add XML and JSON serialization and parsing (I needed JSON)
• Addition of the currency precision in src/lib/currencies.ts
• Addition of a generic model for messages so the lib can be use with less specific inside class knowledge (preview)
• Add a small example file examples/get-account-messages.ts
• Update the Readme

[svapnil]

Thanks for writing this @guenoledc ! Will review it shortly, hopefully by this weekend

[svapnil]

Overall, this PR looks good to me - it doesn't seem like you've changed any existing interfaces, so this change should be backwards compatible as well.

I can merge this request in and update the version so this makes it to the production branch.

Todo on my part aswell will be updating the docs: docs.iso20022js.com.

[guenoledc]

Thanks for the update

Just be sure in the doc that it is mentioned that only a subset of the iso camt.003, 4, 5, 6 specifications are covered.

Happy to have contributed and will do so again when we have other changes