OandA StopLimit orders

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Expected Behavior

Stop Limit orders work

Actual Behavior

Stop Limit orders are NotSupported

Potential Solution

Implement Stop Limit orders for OandA

Checklist

• I have completely filled out this template
• I have confirmed that this issue exists on the current master branch
• I have confirmed that this is not a duplicate issue by searching issues

• I have provided detailed steps to reproduce the issue

What are the technical limitations on implementing this?
I can see that OandA provides this, but it's kind of a "hidden" feature.
In OandA you can choose a stop order, and then select "Lower bound/Upper bound", which lets you enter for example 2 pips. This is exactly the same as a StopLimit order, where the limit is 2 pips away from the stop. This functionality would be helpful to ensure prices get filled with reduced slippage.