ESD-1687: Expose as-override on VXC BGP connections

[Phil-Browne]

Wires the SDK's new AsOverride *bool on vRouter BGP connections (added in megaportgo v1.17.0) through the CLI. This was the one remaining BGP field the CLI didn't read or send, so MCR eBGP peering can now be configured end to end, matching the Terraform provider's as_override.

• Bump megaportgo pin v1.15.0 to v1.17.0.
• JSON input: read asOverride in parseBGPConnections, setting the pointer only when the key is present.
• Interactive input: add an optional AS Override prompt that leaves the field unset when skipped.
• Preserve the tri-state: nil means the API applies its default, so existing configs are unaffected.
• Cover the JSON true/false/unset/non-boolean cases and the interactive yes/no/skip/invalid cases in unit tests.

BGP connections are only supplied via JSON or interactive input, so there is no flag-mode work. The JSON path is shared by both VXC buy and update.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
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Additional details and impacted files

@@           Coverage Diff           @@
##             main     #546   +/-   ##
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  Coverage        ?   79.50%           
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  Files           ?      193           
  Lines           ?    18876           
  Branches        ?        0           
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  Hits            ?    15007           
  Misses          ?     2820           
  Partials        ?     1049           

Files with missing lines	Coverage Δ
internal/commands/vxc/vxc_inputs_partner.go	83.22% <100.00%> (ø)
internal/commands/vxc/vxc_prompts_vrouter.go	56.16% <100.00%> (ø)

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[Copilot]

Pull request overview

This PR exposes the Megaport SDK’s new tri-state AsOverride *bool field on vRouter BGP connections through the CLI’s JSON and interactive input paths, enabling end-to-end configuration for MCR eBGP peering.

Changes:

• Bumps github.com/megaport/megaportgo from v1.15.0 to v1.17.0.
• Adds asOverride support to vRouter BGP interactive prompts and JSON parsing while preserving tri-state semantics (nil => API default).
• Extends unit tests to cover asOverride in both interactive and JSON workflows (true/false/unset + invalid types/inputs).

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
internal/commands/vxc/vxc_prompts_vrouter.go	Adds an interactive prompt to optionally set AsOverride on BGP connections.
internal/commands/vxc/vxc_prompts_test.go	Updates/extends prompt tests to validate AsOverride yes/no/skip/invalid behaviors.
internal/commands/vxc/vxc_inputs_partner.go	Parses JSON asOverride and sets AsOverride pointer only when the key is present.
internal/commands/vxc/vxc_inputs_test.go	Adds JSON parsing test coverage for asOverride true/false/unset and type errors.
go.mod	Updates the megaportgo dependency pin to v1.17.0.
go.sum	Updates dependency checksums to match megaportgo v1.17.0.