Enhance address space handling to accept numeric CIDR masks

[JC-wk]

Resolves #4733

What is being addressed

Describe the current behavior you are modifying. Please also remember to update any impacted documentation.

How is this addressed

• Accepts cidr values as strings from "16" to "29" for subnet creation
• Updates documentation
• Updates CHANGELOG.md
• Updates API version
• Adds Tests

[github-actions]

Unit Test Results

677 tests   677 ✅  8s ⏱️
  1 suites    0 💤
  1 files      0 ❌

Results for commit 64afc10.

♻️ This comment has been updated with latest results.

[JC-wk]

I've tested allocating a /27 and that worked in my environment

[Copilot]

Pull request overview

Adds support in the API for requesting auto-assigned address spaces using numeric CIDR prefix lengths (as strings), extending beyond the existing small/medium/large presets while keeping backwards compatibility.

Changes:

• Extend address space allocation logic to accept numeric CIDR masks (string values) and validate allowed ranges.
• Add repository tests for numeric CIDR prefix requests.
• Update workspace authoring documentation and the project changelog to describe the new behavior.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
docs/tre-workspace-authors/authoring-workspace-templates.md	Documents numeric CIDR mask support for address_space_size when requesting additional address spaces.
CHANGELOG.md	Records the enhancement in the unreleased changelog.
api_app/tests_ma/test_db/test_repositories/test_workpaces_repository.py	Adds tests covering successful numeric CIDR prefix requests.
api_app/models/schemas/workspace_template.py	Updates sample schema description text to mention numeric CIDR masks.
api_app/db/repositories/workspaces.py	Implements numeric CIDR prefix parsing/validation and routes it into new CIDR allocation.