Automatically update security release node's short description with SA

Problem/Motivation

When an SA is published the release node is automatically updated with a link to the SA. Someone looking at the project page doesn't know that a specific release is for an SA unless the project admin, or DST member, updates the "short description" to mention it.

Proposed resolution

If a release node's "Short description" field (field_release_short_description) is blank when the SA is published, the field is automatically updated to e.g. "Resolves [SA NAME]".

Remaining tasks

If a release node's "Short description" field (field_release_short_description) is blank when the SA is published, the field is automatically updated to e.g. "Resolves [SA NAME]".

User interface changes

A release node's blank "Short description" says "Resolves [SA NAME]", so that this is shown on the project page.

API changes

n/a

Data model changes

n/a