fix(oauth): add client_id to exchangeCodeForToken + extend unit tests

[Theosakamg]

Summary

Align Node.js SDK with PHP SDK on the api_token grant request and extend unit test coverage.

Bug fix — client_id missing from exchangeCodeForToken()

The PHP SDK sends client_id in both the api_token and refresh_token grants. The Node.js SDK was only sending it in refresh_token. This adds client_id to the URLSearchParams of the api_token grant in src/core/oauth-provider.ts.

const params = new URLSearchParams({
  grant_type: 'api_token',
  api_token: this.clientSecret,
  client_id: this.clientId,  // ← added
});

Unit tests extended

tests/unit/core/oauth2-client.test.ts (+2 changes):

• Updated existing test to assert client_id is present in the api_token grant body
• Added new test: refreshAccessToken throws 'No refresh token available' when called without a stored refresh token (covers the defensive guard on line 121)

tests/unit/upsun-client.test.ts (+14 new tests):

• createAuthRetryMiddleware: non-401 pass-through, 401 triggers forceRefresh() + retry, __upsunRetry double-retry guard, bearer-only mode (no this.auth)
• getUserId: fetches and caches user ID
• getToken: bearer path returns token, throws when no auth method available
• authenticate: throws without API key, returns true on success
• cloneHeaders: handles undefined, Headers instance, array pairs, plain object

Coverage

File	Statements	Branches	Functions	Lines
src/core/oauth-provider.ts	100%	100%	100%	100%
src/upsun.ts	100%	96%*	100%	100%

*96% branches: init || {} defensive fallback on line 312 — unreachable through the generated API stack, acceptable.

618 unit tests passing, 0 failures.

[github-actions]

Upsun SDK checker report

Display raw output

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  SDK Signature Comparison Report
════════════════════════════════════════════════════════════════════════════════


📦 Class: DomainsTask
   Languages: node, php
────────────────────────────────────────────────────────────────────────────────

  ⚠️  Signature Differences:

     Method: add()
       node: (projectId: string, domain: string)
       php: (projectId: string, domainCreateInput: DomainCreateInput)

📦 Class: EnvironmentsTask
   Languages: node, php
────────────────────────────────────────────────────────────────────────────────

  ⚠️  Signature Differences:

     Method: init()
       node: (projectId: string, environmentId: string, profile: string, repository: string, files: FilesInner[])
       php: (projectId: string, environmentId: string, profile: string, repository: string, fileMode: string, filePath: string, fileContents: string)

     Method: addDomain()
       node: (projectId: string, environmentId: string, domainName: string)
       php: (projectId: string, domainCreateInput: DomainCreateInput)

📦 Class: IntegrationsTask
   Languages: node, php
────────────────────────────────────────────────────────────────────────────────

  ⚠️  Signature Differences:

     Method: createIntegration()
       node: (projectId: string, type: string, params: IntegrationCreateData)
       php: (projectId: string, integrationCreateInput: IntegrationCreateCreateInput)

     Method: updateIntegration()
       node: (projectId: string, integrationId: string, type: string, params: IntegrationCreateData)
       php: (projectId: string, integrationId: string, integrationUpdateInput: IntegrationPatch)

📦 Class: MetricsTask
   Languages: node, php
────────────────────────────────────────────────────────────────────────────────

  ⚠️  Missing Methods:
     php:
       - fetchMetrics()

📦 Class: ProjectsTask
   Languages: node, php
────────────────────────────────────────────────────────────────────────────────

  ⚠️  Signature Differences:

     Method: updateSettings()
       node: (projectId: string, settings: ProjectSettings)
       php: (projectId: string)

════════════════════════════════════════════════════════════════════════════════
  Summary
────────────────────────────────────────────────────────────────────────────────
  Total classes analyzed: 26
  ⚠️  Found 7 issue(s)
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