SYN-6862: remove decommissioned v1 (Rigor) client and update README

[jcsco]

Summary

• Deletes the entire syntheticsclient/ package (19 files, ~1,970 lines): the deprecated v1 client for the retired monitoring-api.rigor.com public API, its models, and its unit tests.
• Removes the v1-specific COVERPKG carve-out from the Makefile and the corresponding comment from .testcoverage.yml; the whole module (now just syntheticsclientv2) is measured for coverage.
• Rewrites the README to document only the supported syntheticsclientv2 client: corrects the go get install command to the actual /v2 module path (go get github.com/splunk/syntheticsclient/v2), adds an explicit token/realm configuration section, and drops the Rigor branding/links.
• syntheticsclientv2 behavior is unchanged — no production code in that package was touched.

Compatibility / release impact

• Breaking change: this removes a public Go package (github.com/splunk/syntheticsclient/v2/syntheticsclient) from the module. Any consumer still importing that subpackage directly (rather than syntheticsclientv2) will fail to build after upgrading past this change.
• The v1 client had already been marked deprecated in the README and excluded from coverage/build gating ahead of the Rigor decommission (see the v3 convergence merge, commit 6fc7a64), so this completes that planned removal rather than introducing a new one.
• This tree must not be tagged under the current /v2 module path. Per Go's module major-version rules, removing a public package breaks the compatibility promise of the existing v2.x line, and tagging it v3.0.0 would also be invalid as-is, since a v3 release requires the module path itself to read .../v3 (go.mod still says /v2). This PR does not perform that module-path bump — it's tracked as a follow-up before any tag is cut from this branch. Until that lands, main should not be released.
• Existing v2.x consumers (e.g. terraform-provider-synthetics, pinned to v2.x) are unaffected: the frozen v2 branch/tags are untouched by this change.
• syntheticsclientv2's public API is unchanged, so no consumer of the supported client needs to change their code once the eventual v3 release ships.

Test plan

• Case-insensitive scan confirms no remaining references to Rigor, monitoring-api.rigor.com, or monitoring.rigor.com in the repo.
• make fmtcheck, make vet, make build pass.
• make test-cover passes; syntheticsclientv2 coverage is 94.5% (floor is 90%).
• make test-race passes.
• make lint (golangci-lint v2.12.2) reports 0 issues.
• make govulncheck reports no vulnerabilities.
• make actionlint passes.

Refs: https://splunk.atlassian.net/browse/SYN-6862

🤖 Generated with Claude Code

[github-actions]

CLA Assistant Lite bot CLA Assistant Lite bot All contributors have signed the COC ✍️ ✅

[github-actions]

Code Coverage Report:

Total coverage threshold (90%) satisfied:	PASS
Total test coverage: 94.5% (942/997)

No coverage changes in any files compared to the base.

[chatgpt-codex-connector]

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[jcsco]

recheck

[github-actions]

Integration Test: ✅ Passed

View run

Live integration tests — Total: 60 | Passed: 60 | Failed: 0 | Skipped: 0

Test	Result	Duration (s)
TestLiveApiCheckCreateUpdateAndDeleteV2	✅ Pass	1.26
TestLiveBrowserCheckCreateUpdateAndDeleteV2	✅ Pass	1.37
TestLiveCaCertificateCreateUpdateAndDeleteV2	✅ Pass	0.99
TestLiveClientCertificateCreateUpdateAndDeleteV2	✅ Pass	0.99
TestLiveCreateApiCheckV2	✅ Pass	0.43
TestLiveCreateBrowserCheckV2	✅ Pass	0.47
TestLiveCreateCaCertificateV2	✅ Pass	0.42
TestLiveCreateClientCertificateV2	✅ Pass	0.42
TestLiveCreateHttpCheckV2	✅ Pass	0.44
TestLiveCreateLocationV2	✅ Pass	0.4
TestLiveCreatePortCheckV2	✅ Pass	0.45
TestLiveCreateSslCheckV2	✅ Pass	0.43
TestLiveCreateTotpVariableV2	✅ Pass	0.4
TestLiveCreateVariableV2	✅ Pass	0.4
TestLiveCreateVariableV2ReturnsErrorOnDuplicateName	✅ Pass	0.6
TestLiveDeleteApiCheckV2	✅ Pass	0.42
TestLiveDeleteApiCheckV2ReturnsErrorForNonexistentID	✅ Pass	0.21
TestLiveDeleteBrowserCheckV2	✅ Pass	0.46
TestLiveDeleteCaCertificateV2	✅ Pass	0.4
TestLiveDeleteClientCertificateV2	✅ Pass	0.43
TestLiveDeleteHttpCheckV2	✅ Pass	0.42
TestLiveDeleteLocationV2	✅ Pass	0.45
TestLiveDeletePortCheckV2	✅ Pass	0.42
TestLiveDeleteSslCheckV2	✅ Pass	0.43
TestLiveDeleteTotpVariableV2	✅ Pass	0.39
TestLiveDeleteVariableV2	✅ Pass	0.39
TestLiveDowntimeConfigurationCreateUpdateAndDeleteV2	✅ Pass	1.44
TestLiveGetApiCheckV2	✅ Pass	0.65
TestLiveGetBrowserCheckV2	✅ Pass	0.64
TestLiveGetCaCertificateV2	✅ Pass	0.62
TestLiveGetChecksV2	✅ Pass	0.57
TestLiveGetChromeFlags	✅ Pass	0.21
TestLiveGetClientCertificateV2	✅ Pass	0.64
TestLiveGetDevicesV2	✅ Pass	0.2
TestLiveGetDowntimeConfigurationsV2	✅ Pass	1.06
TestLiveGetExcludedFileTypesV2	✅ Pass	0.19
TestLiveGetHttpCheckV2	✅ Pass	0.63
TestLiveGetHttpCheckV2ReturnsErrorForNonexistentID	✅ Pass	0.19
TestLiveGetLocationsV2	✅ Pass	0.19
TestLiveGetLocationV2	✅ Pass	0.19
TestLiveGetPortCheckV2	✅ Pass	0.62
TestLiveGetSslCheckV2	✅ Pass	0.67
TestLiveGetTotpVariableV2	✅ Pass	0.6
TestLiveGetVariablesV2	✅ Pass	0.58
TestLiveGetVariableV2	✅ Pass	0.58
TestLiveGetVariableV2ReturnsErrorForNonexistentID	✅ Pass	0.19
TestLiveHttpCheckCreateUpdateDeleteV2	✅ Pass	1.31
TestLiveHttpCheckWithNullablePortCreateUpdateAndDeleteV2	✅ Pass	0.9
TestLivePortCheckCreateUpdateAndDeleteV2	✅ Pass	1.28
TestLiveSslCheckCreateUpdateAndDeleteV2	✅ Pass	0.91
TestLiveTotpVariableCreateUpdateAndDeleteV2	✅ Pass	1
TestLiveUpdateApiCheckV2	✅ Pass	0.64
TestLiveUpdateBrowserCheckV2	✅ Pass	0.72
TestLiveUpdateCaCertificateV2	✅ Pass	0.77
TestLiveUpdateClientCertificateV2	✅ Pass	0.86
TestLiveUpdateHttpCheckV2	✅ Pass	0.66
TestLiveUpdatePortCheckV2	✅ Pass	0.64
TestLiveUpdateSslCheckV2	✅ Pass	0.89
TestLiveUpdateTotpVariableV2	✅ Pass	0.81
TestLiveUpdateVariableV2	✅ Pass	0.62