docs: update http source documentation

[vaibhavtiwari33]

http source documentation should be updated to include information regarding available configuration on port value

[JagjotB]

I’d like to take this up. I’ll add documentation for the configurable HTTP source port introduced in #3335, including usage examples and context.

[vaibhavtiwari33]

Let me assign this to you. Please note that the spec for http source configuration was further changed in #3341 , use that for reference instead.