feat: add support for setting start-time

[netr0m]

Description

Adds support for specifying the start time, i.e. to schedule activation.

• Resolves Support for setting start time #80

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

Checklist:

• I have read the contribution guidelines
• My changes follow the Styleguide of this project
• I have run the pre-commit hooks included in this repository
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• All GitHub Actions workflows for this branch/PR have run successfully

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