assertionInfo.WarningInfo.InvalidTime using time finer than milliseconds

[daniilstrata]

In VerifyAssertionConditions in validate.go, notBefore and notOnOrAfter are doing time comparison finer than milliseconds.
According to SAML Core spec

1.3.3 Time Values
All SAML time values have the type xs:dateTime, which is built in to the W3C XML Schema Datatypes
specification [Schema2], and MUST be expressed in UTC form, with no time zone component.
SAML system entities SHOULD NOT rely on time resolution finer than milliseconds. Implementations
MUST NOT generate time instants that specify leap seconds.

TIme comparisons SHOULD NOT rely on time resolution finer than milliseconds.

In our case, the now clock returned 20:08:46.518691 and the notBefore SAML assertion had 20:08:46.55 which triggered the warning. The library should at most compare one significant digit after the seconds dot.

This is a major issue that causes intermittent login failure for users.