Adding minimum fee calculation & validation

[BHouwens]

Description

Adds the minimum fee calculation, which is currently based on the proposed listing price of $0.25 and intends to set the network fee in dollar terms to $0.002.

Changelog

• Adds minimum fee calculation
• Adds minimum fee validation
• Sets fee to a constant for now, where the constant is a TokenAmount == 72072

Type of Change

Please mark the appropriate option by putting an "x" inside the brackets:

• Bug fix
• New feature
• Enhancement or optimization
• Documentation update
• Other (please specify)

Checklist

Put an "x" in the boxes that apply. If you're unsure about any of these, don't hesitate to ask. We're here to help!

• I have tested the changes locally and they work as expected.
• I have added necessary documentation or updated existing documentation.
• My code follows the project's coding standards and style guidelines.
• I have added/updated relevant tests to ensure the changes are properly covered.
• I have checked for and resolved any merge conflicts.
• My commits have clear and descriptive messages.