feat(llc): add support for polls api

[xsahil03x]

This pull request introduces significant changes to the stream_chat package, primarily focused on adding support for poll-related functionalities. The most important changes include adding event listeners for poll events, implementing methods for poll operations in the StreamChatClient class, and creating a new PollsApi class to handle poll-related API calls.

Poll Events and Listeners:

• Added several poll event listeners in the ChannelClientState class, including _listenPollUpdated, _listenPollClosed, _listenPollAnswerCasted, _listenPollVoteCasted, _listenPollVoteChanged, _listenPollAnswerRemoved, and _listenPollVoteRemoved. These listeners handle various poll-related events and update the poll messages accordingly. [1] [2]

Poll Operations in StreamChatClient:

• Introduced methods in the StreamChatClient class to create, retrieve, update, partially update, delete, close polls, and manage poll options and votes. These methods include createPoll, getPoll, updatePoll, partialUpdatePoll, deletePoll, closePoll, createPollOption, getPollOption, updatePollOption, deletePollOption, castPollVote, addPollAnswer, removePollVote, queryPolls, and queryPollVotes.

New PollsApi Class:

• Created a new PollsApi class to define the API operations for polls, including methods for creating, retrieving, updating, partially updating, deleting polls, managing poll options, casting and removing votes, and querying polls and poll votes.

Event Stream Mapping:

• Modified the eventStream getter in the StreamChatClient class to map poll vote events to specific poll answer events, making it easier to handle these events in the state.

Import Statements:

• Updated import statements to include necessary poll-related models in various files, such as client.dart and responses.dart. [1] [2]

These changes enhance the stream_chat package by adding comprehensive support for poll functionalities, including event handling, API operations, and state management.

[codecov]

Codecov Report

Attention: Patch coverage is 50.28902% with 172 lines in your changes missing coverage. Please review.

Project coverage is 60.10%. Comparing base (aacaba6) to head (2d429da).
Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
packages/stream_chat/lib/src/client/channel.dart	19.81%	85 Missing ⚠️
packages/stream_chat/lib/src/core/models/poll.dart	10.00%	72 Missing ⚠️
...ges/stream_chat/lib/src/core/models/poll_vote.dart	38.88%	11 Missing ⚠️
packages/stream_chat/lib/src/client/client.dart	94.73%	2 Missing ⚠️
...s/stream_chat/lib/src/core/models/poll_option.dart	75.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2040      +/-   ##
==========================================
- Coverage   60.27%   60.10%   -0.18%     
==========================================
  Files         318      322       +4     
  Lines       18581    18926     +345     
==========================================
+ Hits        11200    11375     +175     
- Misses       7381     7551     +170     

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