N-02 ERC-20 Approval Issues

[sparrowDom]

Audit notes:

• A single approval is used to grant the approval for an asset token. However, an asset
  token like USDT can be non-compliant and may revert if the approval is not reset before
  this approval call. This may block repeated execution of safeApproveAllTokens .
  Although the LST tokens used in the current strategy do not have this issue, if the code
  is extended to also use Balancer strategies for other assets (e.g., for the tokens backing
  OUSD), this may become an issue. Consider documenting this possibility or renaming
  the function to _approveERC20CompliantAsset . Alternatively, consider following the
  double approval pattern.
• A double approval is used for the BPT. However, this is unnecessary as the BPTs are
  ERC-20-compliant tokens. Consider only doing one approve in this case.

[github-actions]

	Warnings
⚠️	👀 This PR needs at least 2 reviewers

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