[VertexAI] Incorrect API endpoint generated when location is "global"

[minkichoe-lbox]

Environment details

1. API: vertexai
2. OS type and version: N/A (code-level issue)
3. Java version: N/A
4. Version(s): Affects current main branch (commit c70c873)

Description

When location is set to "global", the VertexAI class generates an incorrect API endpoint.

Current behavior:
The endpoint is constructed as global-aiplatform.googleapis.com

Expected behavior:
The endpoint should be aiplatform.googleapis.com (without the global- prefix)

Steps to reproduce

1. Create a VertexAI instance with location set to "global"
2. Observe the generated apiEndpoint

Code example

// Current implementation in VertexAI.java
this.apiEndpoint =
    apiEndpoint.orElse(String.format("%s-aiplatform.googleapis.com", this.location));

// When location = "global", this produces:
// "global-aiplatform.googleapis.com" (incorrect)

// Expected:
// "aiplatform.googleapis.com"

Suggested fix

this.apiEndpoint = apiEndpoint.orElse(
    "global".equals(this.location)
        ? "aiplatform.googleapis.com"
        : String.format("%s-aiplatform.googleapis.com", this.location)
);

External references

• Vertex AI locations documentation

Additional information

The global endpoint aiplatform.googleapis.com is used for accessing Vertex AI resources that are available globally, and it does not follow the regional endpoint pattern of {location}-aiplatform.googleapis.com.

[SivamuruganP]

Raised a PR with the fix
#11853