Enable and add missing doc tests against sandbox API

[c12i]

Closes #82 Closes #37

Changes

• Enable and move doc tests to /docs/**/*.md
• Enable doc tests in the README.md file
• Remove examples from README.md and replace with table that links to the new docs in docs/client, see new README.md
• Reference new Safaricom docs

Fixes

• Fix typo in c2b_register response that did not account for a typo in the actual API response leading to deserialization errors
• Add Reversal = 11 IndentifierType that is required for the transaction_reversal api, the original default ShortCode = 4 always produced a 400 error
• Fix 400 response without a body when sending a dynamic_qr request where the amount is a f64 type. The API only expects this field to be a number (or its string representation) but not a decimal. cc @itsyaasir

TODO

• [x] Try cargo nextest to handle flaky tests -> doc tests not supported, therefore we won't benefit from the retry capabilities nextest provides
• [x] Enable bill_manager API doc tests, tests added but not ran because of inconsistency between our sdk and current api implementation

Findings

• https://github.com/c12i/mpesa-rust/pull/90#issuecomment-1818705150

[c12i]

Flaky tests:

• c2b register -> temporarliy added no_run
• ~transaction reversal: returns a Invalid RecieverIdentifierType error~ - [FIXED] the issue seems to be use of an unsupported RecieverIdentifierType

[c12i]

The C2b simulate API seems to not exist in the docs anymore

[c12i]

Hey @crispinkoech I noticed that whenever I call the bill_manager APIs in sandbox, I get a 401 invalid access token error. Is this something you had encountered when you tested this out?

[c12i]

Hey @crispinkoech I noticed that whenever I call the bill_manager APIs in sandbox, I get a 401 invalid access token error. Is this something you had encountered when you tested this out?

Just realized the current app I am using to make this call does not have access to the bill manager APIs

[crispinkoech]

Hey @crispinkoech I noticed that whenever I call the bill_manager APIs in sandbox, I get a 401 invalid access token error. Is this something you had encountered when you tested this out?

I don't recall, it's been a while 😅

[c12i]

Hey @crispinkoech I noticed that whenever I call the bill_manager APIs in sandbox, I get a 401 invalid access token error. Is this something you had encountered when you tested this out?

I don't recall, it's been a while 😅

No worries, I figured out the cause, my app did not have access to bill manager.

ION, the bill manager api is due for a refactor, I noticed that there are some new changes to the APIs that break the current implementation, will create an issue for this.

[crispinkoech]

No worries. You can assign that to me (as well as the other issue I created, seems I don't have access for that)

[itsyaasir]

@c12i Quick suggestion; The docs are looking good, should we add more information to the module about the service itself, maybe example response or example request ?

We can include the docs in the module itself, something like #![doc = include_str!("../../docs/client/dynamic_qr.md")]