ekump/add config gaps from transport proc (#3350)

Remove support for configuring agent transport via a custom proc. Add ability to set SSL, timeout, and UDS path for agent transport programatically. 
---------

Co-authored-by: Austin Lai <76412946+alai97@users.noreply.github.com>
Co-authored-by: ekump <ekump@users.noreply.github.com>

benchmarks/profiler_http_transport.rb

@@ -29,12 +29,11 @@ def initialize
 
     @transport = Datadog::Profiling::HttpTransport.new(
       agent_settings: Datadog::Core::Configuration::AgentSettingsResolver::AgentSettings.new(
-        adapter: Datadog::Core::Transport::Ext::HTTP::ADAPTER,
+        adapter: Datadog::Core::Configuration::Ext::Agent::HTTP::ADAPTER,
         uds_path: nil,
         ssl: false,
         hostname: '127.0.0.1',
         port: @port,
-        deprecated_for_removal_transport_configuration_proc: nil,
         timeout_seconds: nil,
       ),
       site: nil,

docs/GettingStarted.md

@@ -198,7 +198,7 @@ If your Datadog Agent is listening at any of these locations, no further configu
 If your Agent runs on a different host or container than your application, or you would like to send traces via a different protocol, you will need to configure your application accordingly.
 
   - [How to send trace data via HTTP over TCP to Agent](#changing-default-agent-hostname-and-port)
-  - [How to send trace data via Unix Domain Socket (UDS) to Agent](#using-the-unix-domain-socket-uds-adapter)
+  - [How to send trace data via Unix Domain Socket (UDS) to Agent](#unix-domain-socket-uds)
 
 ### Final steps for installation
 
@@ -2470,62 +2470,42 @@ end
 
 See [Additional Configuration](#additional-configuration) for more details.
 
-#### Using the Net::HTTP adapter
+#### Agent connection methods
+The agent supports communication via TCP or Unix Domain Socket (UDS). The tracer will automatically detect the agent's
+connection method based on the configuration provided.
 
-The `Net` adapter submits traces using `Net::HTTP` over TCP. It is the default transport adapter.
-
-```ruby
-Datadog.configure do |c|
-  c.tracing.transport_options = proc { |t|
-    # Hostname, port, and additional options. :timeout is in seconds.
-    t.adapter :net_http, '127.0.0.1', 8126, timeout: 30
-  }
-end
-```
-
-#### Using the Unix Domain Socket (UDS) adapter
-
-The `UnixSocket` adapter submits traces using `Net::HTTP` over Unix socket.
+##### TCP
+The tracer will connect to the agent via TCP if the `host` and `port` are set, or if `HTTP/HTTPS` is specified as the
+protocol in `DD_TRACE_AGENT_URL`. TCP is the default connection method.
 
+##### Unix Domain Socket (UDS)
 To use, first configure your trace Agent to listen by Unix socket, then configure the tracer with:
 
 ```ruby
 Datadog.configure do |c|
-  c.tracing.transport_options = proc { |t|
-    # Provide local path to trace Agent Unix socket
-    t.adapter :unix, '/tmp/ddagent/trace.sock'
-  }
+  # Provide local path to trace Agent Unix socket
+  c.agent.uds_path = '/tmp/ddagent/trace.sock'
 end
 ```
 
-#### Using the transport test adapter
+You can also define the UDS path using the `DD_TRACE_AGENT_URL` environment variable by setting the protocol to `unix`:
 
-The `Test` adapter is a no-op transport that can optionally buffer requests. For use in test suites or other non-production environments.
-
-```ruby
-Datadog.configure do |c|
-  c.tracing.transport_options = proc { |t|
-    # Set transport to no-op mode. Does not retain traces.
-    t.adapter :test
-
-    # Alternatively, you can provide a buffer to examine trace output.
-    # The buffer must respond to '<<'.
-    t.adapter :test, []
-  }
-end
+```bash
+DD_TRACE_AGENT_URL=unix:///tmp/ddagent/trace.sock
 ```
 
-#### Using a custom transport adapter
+Note: You cannot mix UDS and TCP configurations. If you set `c.agent.uds_path`, you must not set `c.agent.host`
+or `c.agent.port`.
+
+#### Transporting in Test Mode
 
-Custom adapters can be configured with:
+When test mode is enabled, the tracer uses a `Test` adapter for no-op transport that can optionally buffer requests in
+test suites or other non-production environments. It is configured by setting `c.tracing.test_mode.enabled` to true.
+This mode only works for tracing.
 
 ```ruby
 Datadog.configure do |c|
-  c.tracing.transport_options = proc { |t|
-    # Initialize and pass an instance of the adapter
-    custom_adapter = CustomAdapter.new
-    t.adapter custom_adapter
-  }
+  c.tracing.test_mode.enabled = true
 end
 ```