fix(realtime): add presence flag

[filipecabaco]

What kind of change does this PR introduce?

add presence flag

[grdsdev]

@filipecabaco it is missing the resubscribe when presence callback is attached.

[coveralls]

Pull Request Test Coverage Report for Build 18101991298

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 22 of 22 (100.0%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.1%) to 80.606%

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Files with Coverage Reduction	New Missed Lines	%
packages/postgrest/lib/src/postgrest_query_builder.dart	1	94.92%

Totals
Change from base Build 17918038339:	0.1%
Covered Lines:	3138
Relevant Lines:	3893

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💛 - Coveralls