fix: Add missing nano part when encoding timestamp to document

[ghostbuster91]

PR Checklist (not all items are relevant to all PRs)

• Added unit-tests (for runtime code)
• Added bootstrapped code + smoke tests (when the rendering logic is modified)
• Added build-plugins integration tests (when reflection loading is required at codegen-time)
• Added alloy compliance tests (when simpleRestJson protocol behaviour is expanded/updated)
• Updated dynamic module to match generated-code behaviour
• Added documentation
• Updated changelog

[ghostbuster91]

thought: I am not really a fan of constructing bigDecimal from string in here but I couldn't think of anything better.

[Baccata]

BigDecimal(ts.epochSecond + 10e-9 * ts.nano) ?

[ghostbuster91]

I should've made myself clearer. I thought about this approach, but I didn't want to use because of potential precision loss issue.

Consider following:

val now = Instant.now()
val epochSecond: Long = now.getEpochSecond
val nano: Int = 999_999_999 // almost 1 second

val result: Double = epochSecond + 1e-9 * nano
println(s"Result with potential precision loss: ${BigDecimal(result)}")

val accurateBigDecimal =
  BigDecimal(epochSecond) + (BigDecimal(nano) * BigDecimal(10).pow(-9))

println(s"Accurate result : ${accurateBigDecimal}")

Which prints:

Result with potential precision loss: 1725278847
Accurate result : 1725278846.999999999

This is still probably a better idea than going through string parsing :)