fix: report a single semantic version in the user agent

[SaiTejaKundety]

Description

Why is this change being made?

1. The version constant did not match what we actually publish. It was built from four separate constants that produced a four-part string like 2.0.2.0, while every release tag and the pkg.go.dev version are three parts (v2.2.0). The constant names were also misleading: VersionNumber held the major and MajorRevisionNumber held the minor.

2. The user agent was sent with the wrong separator. New used middleware.AddUserAgentKey, which sanitizes its whole argument and rewrites / to -.

What is changing?

1. Replaced the four constants with a single Version = "2.2.0" in MAJOR.MINOR.PATCH form.
2. Switched to middleware.AddUserAgentKeyValue, which sanitizes the key and value separately and joins them with /, so the separator survives.
3. Removed releaseVersion() and userAgent(), which existed only to assemble the version from its four parts.
4. Added secretcache/versionInfo_test.go covering the version format and the User-Agent as sent.

Related Links

• Issue #, if available: N/A

Evidence: the SDK's rules function replaces any character outside its allowlist with -, and / is
not allowed.

• AddUserAgentKey sanitizes the whole string, so / becomes - → AwsSecretCache-2.2.0.
• AddUserAgentKeyValue sanitizes the key and value separately, so when it gets joined with key + "/" + value, the / survives → AwsSecretCache/2.2.0.

---

Testing

How was this tested?

1. go build ./..., go vet ./... and gofmt are clean.
2. go test ./secretcache — 39 tests pass, coverage 97.6%. Also passes under -race.
3. New tests confirm the User-Agent on a real request by pointing the SDK at a local endpoint, so the header is checked as sent rather than as configured. No credentials, network access or AWS account required.
4. Each new test was verified to fail when its defect is reintroduced: reverting to AddUserAgentKey, setting Version to 2.2.0.0, and replacing the header instead of appending to it.

When testing locally, provide testing artifact(s):

1. The captured User-Agent before and after the change:

before: aws-sdk-go-v2/1.36.2 ua/2.1 os/macos ... api/secretsmanager#1.34.19 AwsSecretCache-2.2.0 m/E
after:  aws-sdk-go-v2/1.36.2 ua/2.1 os/macos ... api/secretsmanager#1.34.19 AwsSecretCache/2.2.0 m/E

The SDK's own entries are intact in both, confirming our value is appended rather than overwriting the header.

---

Reviewer notes

Breaking change: this removes the exported VersionNumber, MajorRevisionNumber, MinorRevisionNumber and BugfixRevisionNumber constants. Nothing in this repository referenced them and they were not documented in the README, but they were part of the public API. Callers should use Version.

Release note: Version stays at 2.2.0 here, matching the currently published tag v2.2.0. Whoever cuts the next release should bump Version to the new tag as part of that release

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.55%. Comparing base (0f06393) to head (69faf09).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #132      +/-   ##
==========================================
- Coverage   96.59%   96.55%   -0.05%     
==========================================
  Files           7        6       -1     
  Lines         294      290       -4     
==========================================
- Hits          284      280       -4     
  Misses          8        8              
  Partials        2        2              

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