Fetching featured speakers, accepted sessions, public call for speaker by default

[anhanh11001]

Describe the bug
By default, the server should only return featured speakers, accepted sessions, public speakers call when client-side make GET requests. Currently, it also returns pending sessions or private call for speaker.

Additional context
Discussed in: fossasia/open-event-attendee-android#1902 (comment)

[iamareebjamal]

Except featured speakers, everything should be done as @anhanh11001 stated

[mrsaicharan1]

@anhanh11001 I'd like to take this.

[mrsaicharan1]

@anhanh11001 Which endpoint are you talking about?

[iamareebjamal]

@mrsaicharan1 every endpoint which returns sessions or call for speakers