feat: invoice return

[akshayitzme]

This PR adds the functionality for Sales and Purchase Return.

Invoice Return

• Update Schemas for Invoice Return
• Enable Invoice Return
• Tests
• Documentation: docs: invoice returns books_docs#26

Workflow

follows ERPNext's workflow

#	Qty	SINV Outstanding	Return Inv Outstanding	Paid Amt (Pay)	Paid Amt (Receive)
Scenario 1: (F Payment, F Return, F Payment)
Invoice created	2	20	0	0	0
Payment created	2	0	0	0	20
Return issued (Full)	2	0	-20	0	0
Payment created against Return	2	0	0	20	0
Scenario 2: (F Payment, P Return, P Payment)
Invoice created	2	20	0	0	0
Payment created	2	0	0	0	20
Return Issued (Partial)	1	0	-10	0	0
Payment created against Return	1	0	0	10	0
Scenario 3: (N Payment, F Return)
Invoice created	2	20	0	0	0
Return Issued (Full)	2	20	-20	0	0

(F payment: Full Payment, P Payment: Partial Payment, N Payment: No Payment)

[chaoxu]

Is there a timeline on when this can be merged?
This is an essential requirement that is holding me back from adopting frappe book.

[akshayitzme]

Did a self review, LGTM

[mildred]

@akshayitzme When using your code on an existing database, I get an error:

SqliteError alter table Payment add column referenceType text not null - Cannot add a NOT NULL column with default value ...

[akshayitzme]

@akshayitzme When using your code on an existing database, I get an error:

SqliteError alter table Payment add column referenceType text not null - Cannot add a NOT NULL column with default value ...

Hi, Thanks for pointing this out. I haven't tried reproducing it yet.. will do it in the coming days and push fixes if needed.

[akshayitzme]

@akshayitzme When using your code on an existing database, I get an error:

SqliteError alter table Payment add column referenceType text not null - Cannot add a NOT NULL column with default value ...

fixed in #782

[18alantom]

@akshayitzme setting "required": true for this field breaks migrations.

Ideally this field should not be present because a similar field is present on the PaymentFor child table. You should have used that with a single row instead of introducing a new field.

[18alantom]

I suppose 74a81de fixes it, nevertheless it's a redundant field.