Fix: Ensure node ID is null-terminated in hellocluster.c

[deepakrn]

The returned by are not null-terminated strings, but fixed-length buffers. However, expects a null-terminated string for the argument. This commit modifies in to copy the node ID into a null-terminated local buffer before passing it to , preventing potential undefined behavior.

[deepakrn]

The other options I see are:

1. Have ValkeyModule_GetClusterNodesList return null terminated node ids so that they can be used as is for getting the individual node info by calling GetClusterNodeInfo
2. Have GetClusterNodeInfo take in a non-null terminated node-id of length VALKEYMODULE_NODE_ID_LEN. This would mean that extracting the node id can't happen via strlen().

Both the above options would be breaking changes to the module APIs. So, my proposal is to simply have the hellocluster.c send null terminated node-id to GetClusterNodeInfo API.

cc - @murphyjacob4

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.45%. Comparing base (51f871a) to head (4ac9f99).
⚠️ Report is 18 commits behind head on unstable.

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable    #2933      +/-   ##
============================================
- Coverage     72.46%   72.45%   -0.01%     
============================================
  Files           129      129              
  Lines         70530    70530              
============================================
- Hits          51108    51106       -2     
- Misses        19422    19424       +2     

see 8 files with indirect coverage changes

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[zuiderkwast]

2. Have GetClusterNodeInfo take in a non-null terminated node-id of length VALKEYMODULE_NODE_ID_LEN. This would mean that extracting the node id can't happen via strlen().

Both the above options would be breaking changes to the module APIs.

Why is the second option a breaking change?

[deepakrn]

@zuiderkwast - that is a good point. If we change the logic to look for string of length VALKEYMODULE_NODE_ID_LEN instead of reading until NULL, it shouldn't break clients that send valid node IDs with null terminators. I'll make that change. Thanks for the callout!