Support conditional/grouped user_config fields

[bhsf-james-pannell]

Problem

When an MCP server supports multiple authentication methods (e.g. API token, OAuth, SSO), all settings must be shown to the user at once since there's no way to conditionally display fields based on a selection.

This creates a cluttered setup experience — users see 7+ optional fields when they only need 1-3 depending on their auth method.

Proposed Solution

Add support for one or both of:

Option A: Enum/select field type

A new type: "enum" (or type: "select") that renders as a dropdown:

"auth_mode": {
  "type": "enum",
  "title": "Authentication Method",
  "options": ["API Token", "M2M OAuth", "SSO"],
  "required": true
}

Option B: Conditional visibility via depends_on

Allow fields to declare visibility conditions based on other field values:

"api_token": {
  "type": "string",
  "title": "API Token",
  "depends_on": { "auth_mode": "API Token" }
}

Option C: Field groups

Group related fields together visually:

"user_config_groups": [
  { "title": "API Token Auth", "fields": ["api_token"] },
  { "title": "M2M OAuth", "fields": ["oauth_client_id", "oauth_client_secret"] },
  { "title": "SSO (Entra ID)", "fields": ["sso_username", "sso_password", "sso_tenant", "sso_vanity"] }
]

Use Case

An MCP server that supports 3 auth methods with 7 optional fields. Currently we prefix descriptions with [Option 1 — API Token] etc. to help users understand the grouping, but native support would be much better.

Current Workaround

Prefixing field descriptions with group labels like [Option 1 — API Token] to visually indicate which fields belong together.