[fix] [html] oneOf schema display in HTML2 generator

[johnny603]

Description

OpenAPI 3.0 specs with oneOf constructs containing mixed types (string + object) were producing unreadable output in HTML2 documentation
The issue was that technical strings like "oneOf<string,object>" were appearing in the generated HTML instead of human-readable text

Resolves: #4431

Root Cause Analysis

The issue was in the StaticHtml2Generator class which inherits from DefaultCodegen
The parent class's getSchemaType method calls toOneOfName() which returns technical format "oneOf<Type1,Type2>"
This technical format is not suitable for HTML documentation display

Solution Implemented

Added a custom override of the getSchemaType method in StaticHtml2Generator.java
The new method detects oneOf technical formats and converts them to human-readable text
Example transformation: "oneOf<string,object>" → "String or Object"

Key Implementation Details

Detection: Identifies strings starting with "oneOf<" and ending with ">"
Parsing: Extracts individual types from within the brackets
Formatting: Converts technical type names (string → String, object → Object, etc.)
Output: Joins types with " or " for clear, readable documentation

The HTML2 generator will now produce:

Before: oneOf<string,object> (technical, unreadable)
After: String or Object (human-readable, clear)

Mentions

@simllll

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