Fix/remove mandatory name editing

[mclcavalcante]

allow partial updates by removing mandatory name for editing requests for agents, agent groups, and datasets. following these rules:

• If the name is informed, the new name must overwrite the old name
• If the name is omitted, the old name must be maintained.
• If the name is informed with empty, the old name must be maintained.
• If the name is informed with an invalid value, an error must be raised informing that the name doesn't match the pattern required.

[codecov-commenter]

Codecov Report

Base: 4.91% // Head: 64.00% // Increases project coverage by +59.08% 🎉

Coverage data is based on head (144fbad) compared to base (7ef874b).
Patch coverage: 95.55% of modified lines in pull request are covered.

Additional details and impacted files

@@             Coverage Diff              @@
##           develop    #2120       +/-   ##
============================================
+ Coverage     4.91%   64.00%   +59.08%     
============================================
  Files           15       61       +46     
  Lines         1057     4604     +3547     
============================================
+ Hits            52     2947     +2895     
- Misses        1005     1657      +652     

Impacted Files	Coverage Δ
policies/api/http/endpoint.go	96.00% <80.00%> (ø)
policies/policy_service.go	86.15% <80.00%> (ø)
fleet/agent_group_service.go	76.71% <100.00%> (ø)
fleet/agent_service.go	65.51% <100.00%> (ø)
fleet/api/http/endpoint.go	92.48% <100.00%> (ø)
fleet/api/http/requests.go	100.00% <100.00%> (ø)
fleet/postgres/agent_groups.go	81.88% <100.00%> (ø)
sinks/api/http/endpoint.go	97.00% <100.00%> (ø)
sinks/api/http/requests.go	97.95% <100.00%> (ø)
sinks/postgres/sinks.go	73.41% <100.00%> (ø)
... and 77 more

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[lpegoraro]

LGTM