[docs:gsoc26] Documentation for X.509 Certificate generator templates

[stktyagi]

This issue tracks documentation for the GSoC 2026 X.509 Certificate Generator Templates project.

Related implementation issues:

1. [feature:gsoc26] Extend AbstractTemplate for X.509 Certificates #1356
2. [feature:gsoc26] Update Django admin for Certificate templates #1357
3. [feature:gsoc26] Implement certificate lifecycle management and integration #1358
4. [feature:gsoc26] Implement auto-regeneration of certificates on device update #1359
5. [feature:gsoc26] Expose certificate data as template variables #1360
6. [feature:gsoc26] Integrate Certificate Templates into REST API #1361
7. [feature] Introduce DeviceCertificate relational model for standalone certificates #1377
8. [feature:gsoc26] Support custom X.509 extensions with private OIDs during certificate creation django-x509#222

Documentation deliverables from the GSoC proposal

Create a dedicated documentation page for certificate templates covering:

• Overview of what certificate templates are and when to use them.
• Use cases listed in the proposal: HTTPS, 802.1x, mTLS, and device authentication.
• Step-by-step instructions for creating a Certificate Authority.
• Step-by-step instructions for creating a blueprint certificate.
• Step-by-step instructions for creating a certificate template.
• Step-by-step instructions for assigning the template to a device.
• Step-by-step instructions for using certificate variables in configuration templates.
• Template variable reference for certificate PEM, private key PEM, and certificate UUID.
• Lifecycle behavior on assignment, unassignment, renewal, and device property changes.
• Explanation of configurable regeneration behavior after that behavior is decided during implementation.
• Supported options and limitations, including the proposal's out-of-scope items: SAN, OCSP, and Let's Encrypt.
• A short demonstration video.

Static media files, such as images or GIFs, should be added to the docs branch after the implementation of each feature, so the final workflow and functionality can be documented visually.

[nemesifier]

Updated the issue body to make the GSoC proposal coverage explicit. I expanded the documentation checklist with the dedicated docs page, use cases, step-by-step usage, variable reference, lifecycle behavior, limitations, demo video, and static media requirements from the proposal. No design decision was made here.

To review the exact changes, open this issue in the browser, navigate to the top bar of the issue description, click "last edited by nemesifier", then click "most recent". GitHub does not provide a quick URL for that view.