Builds telemetry metadata by merging default, module-level, and action-level metadata.

Metadata precedence (later metadata overwrites earlier on key conflicts):

1. Default metadata: %{module: ctx.module, action: ctx.action}
2. Module-level metadata: Configured via use Axn, metadata: &function/1
3. Action-level metadata: Configured via action :name, metadata: &function/1

All custom metadata functions are called safely and return %{} on error.

Parameters

• ctx - Context struct containing action information
• action_opts - Action-level options (may include :metadata function)
• module_opts - Module-level options (may include :metadata function)

Return Value

Returns a map of telemetry metadata.

Extracts metadata from options.

Looks for the :metadata key in options and safely calls the function if present. Returns empty map if no metadata function or on error.

Wraps step execution with telemetry events.

Emits :telemetry.span/3 events with the following structure:

• Event name: [:axn, :action]
• Start metadata: Default + module + action metadata
• Stop metadata: Same as start, plus any context changes during execution
• Exception metadata: Same as start, plus exception details

Custom metadata functions are called safely and default to %{} on error.

Parameters

• ctx - Initial Context struct
• action_opts - Action-level options (may include :metadata function)
• module_opts - Module-level options (may include :metadata function)
• runner - The function to run the action

Return Value

Returns a Context struct with the final execution state and result.