fix: cast params and respect defaults on join payload

[leandrocp]

• Respect Payloads.Broadcast.Replay default values
• Correctly cast params so "false" is not interpreted as a truth value
• Add tests, spec, and docs

[github-actions]

CRAP Score Report

Summary: files=234 functions=1294 scored=1294 worst_score=15944.76

** (Mix) CRAP threshold failed: max_score=30.00
High scores: 30
  lib/extensions/postgres_cdc_rls/subscription_manager.ex Extensions.PostgresCdcRls.SubscriptionManager.handle_info/2 score=37.16
  lib/realtime/adapters/postgres/oid_database.ex Realtime.Adapters.Postgres.OidDatabase.name_for_type_id/1 score=15944.76
  lib/realtime/application.ex Realtime.Application.setup_region_mapping/0 score=47.11
  lib/realtime/nodes.ex Realtime.Nodes.default_region_mapping/1 score=157.20
  lib/realtime/operations.ex Realtime.Operations.rebalance/0 score=42.00
  lib/realtime/operations.ex Realtime.Operations.kill_connections_to_tenant_id/2 score=90.00
  lib/realtime/tenants/connect.ex Realtime.Tenants.Connect.handle_info/2 score=40.25
  lib/realtime_web/channels/realtime_channel.ex RealtimeWeb.RealtimeChannel.handle_info/2 score=48.69
  lib/realtime_web/channels/realtime_channel.ex RealtimeWeb.RealtimeChannel.handle_in/3 score=132.36
  lib/realtime_web/dashboard/feature_flags.ex RealtimeWeb.Dashboard.FeatureFlags.handle_event/3 score=112.70
  lib/realtime_web/dashboard/node_info.ex RealtimeWeb.Dashboard.NodeInfo.fetch_node_data/2 score=42.00
  lib/realtime_web/dashboard/recon_trace.ex RealtimeWeb.Dashboard.ReconTrace.handle_event/3 score=552.00
  lib/realtime_web/dashboard/recon_trace.ex RealtimeWeb.Dashboard.ReconTrace.handle_info/2 score=210.00
  lib/realtime_web/dashboard/recon_trace.ex RealtimeWeb.Dashboard.ReconTrace.render_value/2 score=42.00
  lib/realtime_web/dashboard/recon_trace.ex RealtimeWeb.Dashboard.ReconTrace.load_module_functions/1 score=42.00
  lib/realtime_web/dashboard/recon_trace.ex RealtimeWeb.Dashboard.ReconTrace.parse_and_start/2 score=110.00
  lib/realtime_web/dashboard/recon_trace.ex RealtimeWeb.Dashboard.ReconTrace.format_value/1 score=702.00
  lib/realtime_web/dashboard/recon_trace.ex RealtimeWeb.Dashboard.ReconTrace.sort_entries/2 score=42.00
  lib/realtime_web/dashboard/recon_trace.ex RealtimeWeb.Dashboard.ReconTrace.parse_module/1 score=90.00
  lib/realtime_web/dashboard/sql_inspector.ex RealtimeWeb.Dashboard.SqlInspector.handle_event/3 score=72.00
  lib/realtime_web/dashboard/sql_inspector.ex RealtimeWeb.Dashboard.SqlInspector.execute_read_only/1 score=72.00
  lib/realtime_web/dashboard/sql_inspector.ex RealtimeWeb.Dashboard.SqlInspector.mask_sensitive_columns/1 score=42.00
  lib/realtime_web/dashboard/sql_inspector.ex RealtimeWeb.Dashboard.SqlInspector.compare_cells/2 score=42.00
  lib/realtime_web/dashboard/sql_inspector.ex RealtimeWeb.Dashboard.SqlInspector.format_cell/1 score=72.00
  lib/realtime_web/dashboard/tenant_migrations.ex RealtimeWeb.Dashboard.TenantMigrations.handle_info/2 score=156.00
  lib/realtime_web/live/components.ex RealtimeWeb.Components.input/1 score=90.00
  lib/realtime_web/live/inspector_live/conn_component.ex RealtimeWeb.InspectorLive.ConnComponent.handle_event/3 score=53.83
  lib/realtime_web/live/inspector_live/event_log_component.ex RealtimeWeb.InspectorLive.EventLogComponent.category_variant/1 score=35.00
  lib/realtime_web/live/inspector_live/event_log_component.ex RealtimeWeb.InspectorLive.EventLogComponent.event_label/1 score=76.13
  lib/realtime_web/live/status_live/index.ex RealtimeWeb.StatusLive.Index.handle_event/3 score=42.00

[coveralls]

No base build to compare — fix-join-payload-defaults into main