Slightly improve serde documentation

[pitdicker]

Fixes #1484.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 91.81%. Comparing base (236b7ad) to head (2d2062f).
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/datetime/serde.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1519   +/-   ##
=======================================
  Coverage   91.81%   91.81%           
=======================================
  Files          40       40           
  Lines       18351    18355    +4     
=======================================
+ Hits        16849    16853    +4     
  Misses       1502     1502           

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[pitdicker]

No clue yet why a warning shows up for the naive::time module on this PR but not on main:

error: redundant explicit link target
   --> src/naive/time/mod.rs:193:18
    |
193 | /// [`DateTime`](crate::DateTime) with fractional minutes as offset, or using
    |      ----------  ^^^^^^^^^^^^^^^ explicit target is redundant
    |      |
    |      because label contains path that resolves to same destination
    |
    = note: when a link's destination is not specified,
            the label is used to resolve intra-doc links
    = note: `-D rustdoc::redundant-explicit-links` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(rustdoc::redundant_explicit_links)]`
help: remove explicit link target
    |
193 | /// [`DateTime`] with fractional minutes as offset, or using
    |     ~~~~~~~~~~~~

[pitdicker]

No clue yet why a warning shows up for the naive::time module on this PR but not on main:

Seems to be a bug in the error reporting of rustdoc. The redundant target was in libs.rs but for a similar DateTime link.

[djc]

This seems weirdly imprecise, and its precision doesn't match the string used for expecting().

[pitdicker]

It is the RFC 3339 format with the addition that it can (de)serialize datetimes outside the 0..=9999 years range using the ISO 8601 syntax. I'll try to word it better.

[djc]

FWIW, it's somewhat on purpose that the first line of docstrings doesn't have a .. These are sentence fragments, not full sentences.

[pitdicker]

Really? Okay.