Add Rate Slippage Per Token for Provider Orders

[chibie]

User Story
As a provider, I want to set a slippage percentage for each token I offer, to have more granular control over price fluctuations and protect my margins per currency pair.

Acceptance Criteria

1. GIVEN a provider is updating a token's settings
   WHEN they include a rate_slippage value
   THEN the value is saved as a decimal on that ProviderOrderToken

2. GIVEN a provider retrieves their profile
   WHEN viewing token details
   THEN they can see the rate_slippage value for each token

3. GIVEN a provider configures a new token
   WHEN no rate_slippage is specified
   THEN it defaults to 0

4. GIVEN a provider configures a new token
   WHEN the rate_slippage is more than 20% of the currency market rate
   THEN it returns an error message

5. GIVEN a lock payment order is being assigned
   WHEN checking rate matches with providers
   THEN use the provider's token-specific slippage instead of hardcoded 0.5

Tech Details

• Add rate_slippage field to ProviderOrderToken entity schema using decimal.Decimal type
• Update the token handling section in UpdateProviderProfile to process rate_slippage
• Update GetProviderProfile to include rate_slippage in token response data
• Add rate_slippage to ProviderOrderTokenPayload type
• Update AssignLockPaymentOrder in PriorityQueueService to:

• Query provider's token slippage during rate matching
• Use token slippage instead of hardcoded 0.5 value
• Handle case where token has default 0 slippage
• Add error logging for slippage lookup failures

Notes/Assumptions

• The field should allow only positive values
• Existing ProviderOrderTokens will have rate_slippage defaulted to 0
• rate_slippage must be <= 20% of the market rate of the fiat currency

Open Questions

• Should we have a system-wide default slippage if token slippage lookup fails?

[Amizeey]

Let me handle this issue!

[Supa-mega]

May I handle this issue? first time contributor

[caxtonacollins]

I'd like to handle this task.

[Emeka000]

Would love to tackle this!

[Atanda1]

@caxtonacollins Are you still gonna work on this? Or, should I reassign it?

[gelluisaac]

Can I jump on this task?

[JuViquez]

Can I try solving this issue?