refactor: Combine interfaces and contracts in InterestBearingToken #15

	# name: Forge Tests Gas Report

	# on:
	# push:
	# branches:
	# - main
	# pull_request:

	# permissions: write-all

	# jobs:
	# check:
	# name: Gas report
	# runs-on: ubuntu-latest
	# steps:
	# - uses: actions/checkout@v4
	# with:
	# submodules: recursive

	# - name: Install Foundry
	# uses: foundry-rs/foundry-toolchain@v1

	# - name: Run Forge build
	# run: \|
	# forge --version
	# make sizes
	# id: build

	# - name: Run Forge tests with gas report
	# run: make gas-report profile=ci
	# env:
	# # make fuzzing semi-deterministic to avoid noisy gas cost estimation
	# # due to non-deterministic fuzzing (but still use pseudo-random fuzzing seeds)
	# FOUNDRY_FUZZ_SEED: 0x${{ github.event.pull_request.base.sha \|\| github.sha }}
	# MNEMONIC: ${{ secrets.MNEMONIC_FOR_TESTS }}
	# MAINNET_RPC_URL: ${{ secrets.MAINNET_RPC_URL }}

	# - name: Compare gas reports
	# uses: Rubilmax/foundry-gas-diff@v3.16
	# id: gas_diff

	# - name: Add gas diff to sticky comment
	# if: github.event_name == 'pull_request' \|\| github.event_name == 'pull_request_target'
	# uses: marocchino/sticky-pull-request-comment@v2
	# with:
	# # delete the comment in case changes no longer impact gas costs
	# delete: ${{ !steps.gas_diff.outputs.markdown }}
	# message: ${{ steps.gas_diff.outputs.markdown }}

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