[REFACTOR] remove unnecessary function from Refunds Validate Flow

[Abhicodes-crypto]

Bug Description

Remove this function validate_uniqueness_of_refund_id_against_merchant_id.
Not required as (refund_id, merchant_id ) unique btree, just insert. if insert fails it is not valid .

Expected Behavior

Not required as (refund_id, merchant_id ) unique btree, just insert. if insert fails it is not valid .

Actual Behavior

Does extra DB calls

Steps To Reproduce

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Context For The Bug

No response

Environment

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If not (or if building/running locally), please provide the following details:

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2. Rust version (output of rustc --version): ``
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Have you spent some time to check if this bug has been raised before?

• I checked and didn't find similar issue

Have you read the Contributing Guidelines?

• I have read the Contributing Guidelines

Are you willing to submit a PR?

Yes I am willing to submit a PR!

[AaronTJDev]

Hi team, can I take this issue?

[Abhicodes-crypto]

Hi @AaronTJDev , You can work on this issue. The task is to remove the function validate_uniqueness_of_refund_id_against_merchant_id

You can get more context from here.
#1521 (comment)

Feel free to ask any queries regarding it.