fix: Fixes the parsing of datetime

[frgfm]

This PR handles the tedious datetime & timezone issues by sanitizing all of them:

• removes tzinfo from datetime when relevant
• parses datetime information that have "Z"
• specifies swagger examples to avoid Z (which indicate UTC timezone --> we want ISO format independent on TZ, thus UTC, but as a convention and not being specifying UTC as if we could pass UTC+2)
• adds test cases
• updates version specifiers of the API & client

Closes #261

[codecov[bot]]

Codecov Report

Merging #262 (6b2d86d) into main (d8f03c9) will increase coverage by 0.08%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #262      +/-   ##
==========================================
+ Coverage   94.98%   95.07%   +0.08%     
==========================================
  Files          60       60              
  Lines        1395     1420      +25     
==========================================
+ Hits         1325     1350      +25     
  Misses         70       70              

Flag	Coverage Δ
client	100.00% <ø> (ø)
unittests	94.80% <100.00%> (+0.09%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/app/schemas/base.py	100.00% <100.00%> (ø)
src/app/schemas/devices.py	100.00% <100.00%> (ø)
src/app/schemas/events.py	100.00% <100.00%> (ø)
src/app/schemas/installations.py	100.00% <100.00%> (ø)