Update golang version to 1.26.3

[esarafianou]

Summary

Bumps Go from 1.25.9 to 1.26.3 across the operator and updates FIPS image references:

• Go toolchain bumped to 1.26.3
• FIPS runtime image cgr.dev/mattermost.com/glibc-openssl-fips bumped to 16.1.0@sha256:3ffd0b8b...

Release Note

Updates Golang to 1.26.3 and bumps FIPS base image (glibc-openssl-fips) to 16.1.0.

Made with Cursor

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR upgrades the Go toolchain from 1.25.x to 1.26.3 across the module declaration, default and FIPS builder images (pinned digests for FIPS), Makefile FIPS variables, and the e2e test container image tag.

Changes

Go 1.26 Upgrade

Layer / File(s)	Summary
Go toolchain version declaration go.mod	Module toolchain directive updated from go 1.25.9 to go 1.26.3.
Build container images and FIPS pinning Dockerfile, Dockerfile.fips, Makefile	Dockerfile default BUILD_IMAGE argument updated to golang:1.26.3; Dockerfile.fips and Makefile FIPS variables updated/pinned to go-msft-fips:1.26.3 and glibc-openssl-fips:16.1.0 with corresponding sha256 digests.
Test environment image test/e2e.sh	E2E test script Docker configuration switched from golang:1.25 to golang:1.26.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and accurately summarizes the main change: updating Go from version 1.25.9 to 1.26.3 across multiple build configuration files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The pull request description accurately describes the changeset: Go version bump from 1.25.9 to 1.26.3 and FIPS image updates, matching the file modifications.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch bump-operator-to-v1.26.3

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@Makefile`:
- Line 18: Replace the mutable tag assigned to BUILD_IMAGE_FIPS with the exact
patch+digest used in Dockerfile.fips so both build paths use the identical image
reference; locate the BUILD_IMAGE_FIPS variable in the Makefile and update its
value from cgr.dev/mattermost.com/go-msft-fips:1.26 to the pinned reference
matching Dockerfile.fips
(1.26.3@sha256:90017f556002f392c7eb21a96bf845e1b0675cb32a43ac8c85c25cbb80e848cc).

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 8f1391f2-13aa-4f61-83c3-0343fbd9a0ea

📥 Commits

Reviewing files that changed from the base of the PR and between 37e2de2 and e9da51a.

📒 Files selected for processing (5)

• Dockerfile
• Dockerfile.fips
• Makefile
• go.mod
• test/e2e.sh

[mm-cloud-bot]

@esarafianou: Adding the "do-not-merge/release-note-label-needed" label because no release-note block was detected, please follow our release note process to remove it.

Details

I understand the commands that are listed here

[carlisgg]

LGTM