rest-assured/src/main/java/io/restassured/config/MultiPartConfig.java
public MultiPartConfig defaultBoundary(String defaultBoundary) {
        return new MultiPartConfig(defaultControlName, defaultFileName, defaultSubtype, defaultBoundary, defaultCharset, true);
    }
public MultiPartConfig defaultBoundary(String defaultBoundary) {
        return new MultiPartConfig(defaultControlName, defaultFileName, defaultSubtype, defaultBoundary, defaultCharset, true);
    }
Specify an explicit default multipart boundary to use when sending multi-part data.

@param defaultBoundary The boundary to set
@return An updated MultiPartConfig