feat: add FRU (Field Replaceable Unit) collector

[Zayden-R]

Summary

Adds a new ipmi-fru collector that exposes hardware inventory data as the ipmi_fru_info Prometheus metric.

Closes #127

What this implements

• New collector_fru.go following the existing collector_bmc.go pattern
• 6 FRU regex patterns + getter functions in freeipmi/freeipmi.go
• Registration in config.go via GetInstance() switch
• Labels: product_name, product_serial, product_manufacturer, product_part_number, board_product_name, chassis_type
• Graceful degradation: missing fields return N/A, never errors
• Opt-in via config (not added to default collectors list)

What is NOT included from #127

This is the core implementation. The following items from the original request are left as follow-up work:

• Per-device FRU entries (PSUs, backplanes, NICs, RAID controllers) -- currently only parses the first/system board entry
• PSU wattage/capacity parsing (rated watts for capacity alerting)
• Manufacturing dates
• DC output specifications
• Native IPMI implementation (collector_fru_native.go)

These can each be added incrementally in future PRs.

Tested on

• Hardware: Dell PowerEdge R730
• OS: RHEL 9.5
• FreeIPMI: 1.6.14
• Go: 1.24.2

# HELP ipmi_fru_info Constant metric with value 1 providing FRU information.
# TYPE ipmi_fru_info gauge
ipmi_fru_info{board_product_name="PowerEdge R730",chassis_type="N/A",product_manufacturer="DELL",product_name="PowerEdge R730",product_part_number="",product_serial="H804B42"} 1
ipmi_up{collector="fru"} 1

Example config

modules:
  default:
    collectors:
      - bmc
      - ipmi
      - chassis
      - fru

Signed-off-by: Zayden R Zayden-R@users.noreply.github.com

[bitfehler]

Hi,

thanks, this looks good. Could I ask you to add a very brief section about this to docs/metrics.md and also add this to the # Available collectors are ... comment in both ipmi_local.yml and ipmi_remote.yml so that people will know/learn about it?