[exporter/datadog] Deprecate logs::dump_payloads (#34490)

**Description:** <Describe what has changed.>
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
Deprecates `logs::dump_payloads` because this config option is invalid
with the Datadog Agent logs pipeline which will be enabled by default in
the following release. This PR will be included in v0.107.0 and
#34420
will be included in v0.108.0.

**Link to tracking Issue:** <Issue number if applicable>

**Testing:** <Describe what testing was performed and which tests were
added.>
The log appears as follows:
```
2024-08-07T14:49:10.514-0400    warn    datadogexporter@v0.106.1/config.go:462  logs::dump_payloads is deprecated and will raise an error if set when the Datadog Agent logs pipeline is enabled by default in collector version v0.108.0    {"kind": "exporter", "data_type": "logs", "name": "datadog"}
```

**Documentation:** <Describe the documentation added.>

---------

Co-authored-by: Yang Song <songy23@users.noreply.github.com>

.chloggen/stanley.liu_deprecate-dump-payloads.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: deprecation
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: exporter/datadog
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Deprecates `logs::dump_payloads` since it is invalid with the Datadog Agent logs pipeline, which will be enabled by default in the v0.108.0 release.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [34490]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

exporter/datadogexporter/config.go

@@ -324,6 +324,7 @@ type LogsConfig struct {
 
 	// DumpPayloads report whether payloads should be dumped when logging level is debug.
 	// Note: this config option does not apply when enabling the `exporter.datadogexporter.UseLogsAgentExporter` feature flag.
+	// Deprecated: This config option is not supported in the Datadog Agent logs pipeline.
 	DumpPayloads bool `mapstructure:"dump_payloads"`
 
 	// UseCompression enables the logs agent to compress logs before sending them.
@@ -668,6 +669,9 @@ func (c *Config) Unmarshal(configMap *confmap.Conf) error {
 			}
 			return fmt.Errorf("%v is not valid when the exporter.datadogexporter.UseLogsAgentExporter feature gate is %v", logsExporterSetting.setting, enabledText)
 		}
+		if logsExporterSetting.setting == "logs::dump_payloads" && logsExporterSetting.valid && configMap.IsSet(logsExporterSetting.setting) {
+			c.warnings = append(c.warnings, fmt.Errorf("%v is deprecated and will raise an error if set when the Datadog Agent logs pipeline is enabled by default in collector version v0.108.0", logsExporterSetting.setting))
+		}
 	}
 
 	return nil