fix: correct schema field type in JQL search responses

[fank]

Summary

• Fixes issue Unable to "expand" schema in new JQL issue search endpoint #404 where the schema field couldn't be unmarshaled when using expand="schema" in JQL searches
• Changes the schema field type from map[string]string to map[string]*IssueFieldSchema
• Affects both v2 and v3 API models

Problem

When fetching issues through the new JQL search endpoint with expand="schema", users received the error:

cannot unmarshal object into Go struct field IssueSearchJQLSchemeV2.schema of type string

The API returns schema as nested objects:

"schema": {
    "summary": {
        "type": "string",
        "system": "summary"
    },
    "assignee": {
        "type": "user",
        "system": "assignee"
    }
}

But the struct incorrectly expected map[string]string.

Changes

• Added IssueFieldSchema struct with Type and System fields
• Updated IssueSearchJQLSchemeV2.Schema to use map[string]*IssueFieldSchema
• Updated IssueSearchJQLScheme.Schema to use map[string]*IssueFieldSchema
• Added unit test to verify correct unmarshaling

Test plan

• Added unit test that verifies schema unmarshaling works correctly
• Test passes with the new struct definition
• Manual testing with actual Jira API (requires credentials)

Fixes #404

🤖 Generated with Claude Code