Add Hedgerow schema

[christinelangston]

Several edits to add data schema for Hedgerow Removal Notice: Added HedgerowRemovalNotice Applicant, Application Data, Proposal, and Property.
Additional edits made to allow for this:

• Made type optional in BaseApplicant (Applicant.ts file)
• Refactor Proposal by redefining ProposalBase

[jessicamcinchak]

Looks great, two minor comments !

[jessicamcinchak]

If we actually want to fully omit description, I think we can alternatively do something like this:

export type HedgerowRemovalNoticeProposal = Pick<ProposalBase, "boundary"> & { 
  reason: string; 
  hedgerowLength: { metres: number };
  hedgerowAgeLessThanThirty: boolean;
}

Which rather than extending the whole ProposalBase will just pick the single optional boundary field and add it to the rest of our custom proposal definition !

[christinelangston]

That makes sense to me! I would defer to you, do you want to omit description here?

[jessicamcinchak]

Let's omit if never actually appears in the service itself as August was clarifying !

[christinelangston]

Made these suggested edits to Proposal.ts

[jessicamcinchak]

nit: I think our proposal.boundary.area always expects both squareMetres and hectares properties?

[christinelangston]

Ah yes, just confirmed hectares are optional. Which makes sense, it passed the tests I ran locally. Would you prefer to have them included?