fix(document-builder): accept multi-digit OpenAPI version segments

[yogeshwaran-c]

What kind of change does this PR introduce?

Bug fix (DocumentBuilder).

What is the current behavior?

DocumentBuilder.setOpenAPIVersion validates its argument with:

if (version.match(/^\d\.\d\.\d$/)) { … }

The regex requires exactly one digit per segment. OpenAPI Specification versions follow semver — 3.0.x has already reached 3.0.4, a future 3.0.10 or 3.10.0 would be entirely valid — but any of those would be silently rejected today with only a warn-level log, and the default version on the document would be kept.

Minimal repro:

const builder = new DocumentBuilder().setOpenAPIVersion('3.0.10');
// builder.build().openapi is still the default (3.0.0), no error,
// only a WARN-level log: 'The OpenApi version is invalid. Expecting format \"x.x.x\"'

What is the new behavior?

Widened the regex to /^\d+\.\d+\.\d+$/, so each segment may contain any non-negative integer. Genuinely malformed inputs (3.0, 3.0.0-beta, …) still fall through to the existing warning.

Additional context

Added three unit-test cases to test/document-builder.spec.ts covering:

• The previously-accepted single-digit case (3.1.0) — regression guard.
• Multi-digit segments (3.0.10, 3.10.0, 10.20.30).
• Malformed inputs, to confirm they still leave the default in place.