fix: m/s replication when using ipv6

[jmtsi]

Description

I couldn't get the master-follower replication working in my IPv6 EKS cluster. When the operator tried to set up the replication, the follower logged errors:

13 Mar 2024 16:46:20.357 * Connecting to MASTER [2a05:d028:10:482:cae3::3]:6379
13 Mar 2024 16:46:20.360 # Unable to connect to MASTER: Resource temporarily unavailable

If I manually ran the slaveof command without using brackets, the replication started successfully:

13 Mar 2024 16:46:21.250 * Connecting to MASTER 2a05:d028:10:482:cae3::3:6379
13 Mar 2024 16:46:21.250 * MASTER <-> REPLICA sync started

This PR modifies the getRedisServerIP function to return the plain IPv6 address, as the brackets should only be added when using <ipv6_addr>:<port> pairs, as per RFC5952.

I also add new function getRedisServerAddress, which handles the address formatting.

Fixes #309, #139

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist

• Tests have been added/modified and all tests pass.
• Functionality/bugs have been confirmed to be unchanged or fixed.
• I have performed a self-review of my own code.
• Documentation has been updated or added where necessary.

Additional Context

This fixes the IPv6 support which was working previously only for the standalone instances.

[codecov]

Codecov Report

Attention: Patch coverage is 42.85714% with 12 lines in your changes are missing coverage. Please review.

Project coverage is 35.75%. Comparing base (d121d86) to head (81a9c23).
Report is 6 commits behind head on master.

Files	Patch %	Lines
k8sutils/cluster-scaling.go	0.00%	8 Missing ⚠️
k8sutils/redis.go	69.23%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #827      +/-   ##
==========================================
+ Coverage   35.20%   35.75%   +0.55%     
==========================================
  Files          19       19              
  Lines        3213     2629     -584     
==========================================
- Hits         1131      940     -191     
+ Misses       2015     1620     -395     
- Partials       67       69       +2     

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[drivebyer]

Thanks for your contribution. I'm not quite sure when to add brackets or not. I noticed that getRedisServerIP in the AddRedisNodeToCluster function is not being replaced. By the way, does Redis Cluster still work fine on IPv6? @jmtsi

[jmtsi]

@drivebyer Good catch! Somehow I missed those from my commit. All the remaining references have now been checked and replaced.

I'll test the cluster-mode with IPv6 today and see that it works without problems.

[jmtsi]

@drivebyer After these latest changes I can successfully create a cluster-mode Redis in my IPv6 cluster and the m/s replication works without problems.

Edit: I noticed that commit authoring was wrong, so force pushed the branch with correct information.