STAC-22970: Validate HTTPS endpoints protected by self-signed certificates or signed with private CA

[viliakov]

Add support for private CA and self-signed certificates in HTTPS connections

This PR adds support for connecting to SUSE Observability instances protected with self-signed certificates or certificates signed by private CAs, providing a secure alternative to the existing --skip-ssl flag.

Summary

Instead of completely disabling SSL verification with --skip-ssl, users can now provide their own self-signed certificates or trusted CA certificates to validate HTTPS connections.
Changes

New Command Line Flags

• --ca-cert-path: Path to a PEM-encoded CA certificate file
• --ca-cert-base64-data: Base64-encoded CA certificate data

Flag Usage Scenarios

• Private CA Certificate from File

sts context save --name staging --url https://staging.internal --api-token token123 --ca-cert-path /path/to/ca.crt
Validates certificates against the provided CA certificate file.

• Private CA Certificate as Base64 Data (New)

sts context save --name staging --url https://staging.internal --api-token token123 --ca-cert-base64-data base64-encoded-certificate-data
Validates certificates against the provided base64-encoded CA certificate.

• File Takes Precedence Over Base64

sts context save --name test --url https://test.local --api-token token123 --ca-cert-path /path/to/ca.crt --ca-cert-base64-data ignored_data
When both flags are provided, --ca-cert-path takes precedence.

• Skip SSL Ignores CA Certificates

sts context save --name unsafe --url https://test.local --api-token token123 --skip-ssl --ca-cert-path /path/to/ca.crt
When --skip-ssl is set, any CA certificate flags are ignored, and SSL verification is completely disabled.

sts context save stores ca-cert data, if provided, to ~/.config/stackstate-cli/config.yaml

For example

config before

    - name: viliakov
      context:
        url: https://viliakov.sandbox.stackstate.io
        api-token: ....
        api-path: /api
        admin-api-path: ""
        skip-ssl: false

go run main.go context save --name viliakov --url https://viliakov.sandbox.stackstate.io --api-token ... --ca-cert-path=/Users/viliakov/Workspace/WIP/STAC-22970/viliakov.sandbox.stackstate.io.crt
✅ Connection verified to https://viliakov.sandbox.stackstate.io (Platform version: 2.3.5)
✅ Saved context: 'viliakov'

config after

    - name: viliakov
      context:
        url: https://viliakov.sandbox.stackstate.io
        api-token: ....
        api-path: /api
        admin-api-path: ""
        skip-ssl: false
        ca-cert-base64-data: 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

[rb3ckers]

Nice job