Bump to version 2.0.0.beta2

[TonyCTHsu]

Added

• Add Agent configuration option: timeout_seconds, uds_path, and use_ssl (ekump/add config gaps from transport proc #3350)
• Tracing: Add lightweight log correlation generation (Improve log correlation performance #3486)
• Tracing: Add span links (feat: Add span links to the Datadog API #3546)
• Tracing: Add span_remote field to TraceDigest (chore(tracing): Adds trace_remote field to TraceDigest #3516)
• Tracing: Add _dd.parent_id to tracestate (w3c: Adds p datadog member to tracestate #3488)
• Tracing: Allow RateSampler with zero sampling rate (Allow RateSampler with a sampling rate of zero #3295)
• Grape: Add on_error settings (on_error settings for grape #3370)

Changed

• Rename gem from ddtrace to datadog (Rename library to datadog #3490)
• Require Ruby >= 2.5 (Remove support for Ruby 2.1, 2.2, 2.3, 2.4 #3291)
• Frozen string literals (Frozen string literals  #3392)
• Startup logs emit when reconfigures (do not restrict startup logs to emit only once #3441)
• Enhance validation for configuration (Stricter validation for integer and float configuration #3332, Ensure service and env are strings #3326)
• Tracing: Propagation style configuration becomes case-insensitive (Case-insensitive propagation style configuration #3299)
• Tracing: Return string for #trace_id and #span_id from Correlation::Identifier (Return string for trace_id and span_id from Correlation::Identifier #3322)
• Elasticsearch: Replace instance configuration from client to transport instance (remove access to patching elasticsearch client directly as it is not supported anymore by elasticsearch #3399)
• Grape: Change error_statuses settings to error_status_codes (on_error settings for grape #3370)
• GraphQL: Instrument with GraphQL::Tracing::DataDogTrace and more (Update GraphQL support #3409, GraphQL: Instrument with GraphQL::Tracing::DataDogTrace #3417, GraphQL changes for 2.0 #3388)
• Rack: Change http proxy span pattern (Change http proxy span pattern #3369)
• Sidekiq: Remove tag_args option and worker specific configuration (Sidekiq: Remove tag_args option  #3396, Sidekiq : Remove worker specific configuration #3402)
• Integrations: Rename error_handler settings to on_error (Rename error_handler settings to on_error  #3341)

Fixed

• Tracing: Fix error_status_codes options (Fix error_status_codes options #3344)

Removed

• Profiling: Remove bin/ddtracerb (Remove bin/ddtracerb #3506)
• Ci-app: Remove datadog-ci gem dependency (Remove CI gem dependency #3288)
• Tracing: Remove SpanOperation aliases (Remove span operation aliases #3330)
• Tracing: Remove b3 style from default propagation (Revert "Add b3 default extraction" #3293)
• Tracing: Minimize sampling API (Minimize sampling API #3423)
• Tracing: Remove client_ip disabled env (Remove client_ip disabled env #3404)
• Tracing: Remove use alias for instrument (Remove use alias for instrument #3403)
• Tracing: OpenTracing, qless removed (Remove qless integration #3398, Remove opentracing support #3443)
• Net/Http: Remove Datadog::Tracing::Contrib::HTTP::Instrumentation.after_request (Remove Datadog::Tracing::Contrib::HTTP::Instrumentation.after_request #3367)
• Rails: Drop support for Rails 3 (Remove support for Rails 3 #3324)
• Rails: Remove exception_controller option (Remove obsolete exception_controller option #3243)
• Remove constants, methods and more (Sinatra :Remove deprecated constants #3401, Remove ddtrace transport constants #3336, remove deprecated lazy method for option_definition #3454, Remove distributed_tracing option namespacing #3338, Remove deprecated HTTP Transport methods #3335, Remove deprecated DD_PROPAGATION_STYLE env vars #3298, Remove deprecated DD_PROPAGATION_STYLE env vars #3297, remove deprecated profiler config options #3309, Remove deprecated B3 configuration style #3294, Remove configuration for priority_sampling #3325, Remove deprecated Headers::Ext #3300)