feat[sse]: make method and body configurable

[vegetablechicken233]

Make HTTP Method configurable and add corresponding test functions.
It should be noted that to ensure backward compatibility, the "method" field does not perform empty validation, but is set to "GET" by default (to align with the old version).
In addition, type of "body" field is temporarily set to "io.Reader" (it seems a bit too early to add support for "any"~

[jeevatkm]

@vegetablechicken233 Thanks for the PR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.82%. Comparing base (e158f04) to head (0aad9f4).

Additional details and impacted files

@@           Coverage Diff           @@
##               v3     #985   +/-   ##
=======================================
  Coverage   99.81%   99.82%           
=======================================
  Files          18       18           
  Lines        3882     3893   +11     
=======================================
+ Hits         3875     3886   +11     
  Misses          5        5           
  Partials        2        2           

Flag	Coverage Δ
unittests	99.82% <100.00%> (+<0.01%)	⬆️

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[vegetablechicken233]

BTW I use "len(es.onEvent) == 0 " check instead of "if _, found := es.onEvent[defaultEventName]" check.

Sometimes the implementation of the sse server is not standard, and there is no event with the type of message.
In my opinion, users should be able to use it as long as they have added any eventListener.

@jeevatkm

[jeevatkm]

BTW I use "len(es.onEvent) == 0 " check instead of "if _, found := es.onEvent[defaultEventName]" check.

Sometimes the implementation of the sse server is not standard, and there is no event with the type of message. In my opinion, users should be able to use it as long as they have added any eventListener.

@jeevatkm

@vegetablechicken233 Can you please create a separate PR for this method check changes?

[vegetablechicken233]

@jeevatkm I created two individual PR for each feature:
#988
#989

Please take the time to review them if you have time. If everything is fine, please close this PR.

[jeevatkm]

Closing this PR in favor of PR #988 and #989