fix: orders with amount>0 cannot be completed without payment

[shreyanshdwivedi]

Fixes #6258

Short description of what this resolves:

When the Stripe/Paypal is not linked but it is selected as a payment option, the completed tickets are generated without payment

Changes proposed in this pull request:

• Adds checks to raise an error if payment_mode == free for order with amount>0
• Verifies if the Stripe or Paypal payment is actually made if it's opted as payment_mode

Checklist

• I have read the Contribution & Best practices Guide and my PR follows them.
• My branch is up-to-date with the Upstream development branch.
• The unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

• All the functions created/modified in this PR contain relevant docstrings.

[codecov]

Codecov Report

Merging #6270 into development will decrease coverage by 0.04%.
The diff coverage is 9.09%.

@@              Coverage Diff               @@
##           development   #6270      +/-   ##
==============================================
- Coverage        65.54%   65.5%   -0.05%     
==============================================
  Files              286     286              
  Lines            14589   14600      +11     
==============================================
+ Hits              9562    9563       +1     
- Misses            5027    5037      +10

Impacted Files	Coverage Δ
app/api/orders.py	28.52% <9.09%> (-0.73%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9fc0c20...c53f8b5. Read the comment docs.

[shreyanshdwivedi]

I will like to point out few things -

• The root cause of the error was that it was sending free order status for orders with amount>0 too and it was unchecked.
  So, I included this check -

    if data.get('payment_mode') == 'free' and data.get('amount') > 0:
            raise ConflictException({'pointer': '/data/attributes/payment-mode'},
                                    "payment-mode cannot be free for order with amount > 0")

• All the props used in function is_payment_valid() for checking stripe and paypal payment are dump only. They are not even called when a normal payment is carried out as the function charge_stripe_order_payment and charge_paypal_order_payment saves the order object there itself so no PATCH request.
  However now, if a client sets payment_mode to stripe/paypal and status to completed, these props will be checked from order object (not data as they are dump_only).
  @iamareebjamal please have a look. Updated the PR with these things in consideration

[shreyanshdwivedi]

@uds5501 @kushthedude @mrsaicharan1 it will be great if you guys can test out this PR

[iamareebjamal]

It should be unprocessable entity, not conflict

[shreyanshdwivedi]

It should be unprocessable entity, not conflict

Made the change

[shreyanshdwivedi]

@iamareebjamal please review