feat: Add OSPF placeholder for OpenConfig

[rgildein]

The Nokia SRL device do not support configuration of OSPFv2 or OSPFv3 throw OpenConfig, only throw native native data schema.

[github-actions]

Merging this branch will not change overall coverage

Impacted Packages	Coverage Δ	🤖
github.com/ironcore-dev/network-operator/internal/provider/openconfig	0.00% (ø)

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Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/ironcore-dev/network-operator/internal/provider/openconfig/ospf.go	0.00% (ø)	3 (+3)	0	3 (+3)

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.

[rgildein]

After discussion with @felix-kaestner we come to conclusion that even better would be not implemented/ added the ospf.go for OpenConfig provider.

Example output of configured not supported rescue.

$ k describe ospf test-ospf | yq '.Status.Conditions'
Last Transition Time: 2026-08-19T08:03:19Z
Message: Provider does not implement provider.OSPFProvider
Reason: NotImplemented
Status: False
Type: Ready
Last Transition Time: 2026-08-19T08:03:19Z
Message: Configured successfully
Observed Generation: 1
Reason: Configured
Status: True
Type: Configured
Last Transition Time: 2026-08-19T08:03:19Z
Message: OSPF is not operational
Observed Generation: 1
Reason: Degraded
Status: False
Type: Operational
Last Transition Time: 2026-08-19T08:03:18Z
Message:
Observed Generation: 1
Reason: NotPaused
Status: False
Type: Paused
$ k get ospf -owide
NAME        ADMIN STATE   DEVICE   INSTANCE   ROUTER-ID   READY   CONFIGURED   OPERATIONAL   PAUSED   ADJACENCIES   AGE
test-ospf   Up            leaf1    UNDERLAY   10.0.0.1    False   True         False         False                  24h

The note about "OSPF not supported on Nokia device via OpenConfig provider" will be added to the documentation via #261.