feat: Add SOAR MCP Case Management Tools

[jshlbrd]

Summary

• Add five new case management tools to the SOAR MCP server: close_case, assign_case, change_case_stage, add_case_tag, remove_case_tag
• Add corresponding endpoint constants, documentation, and tool mapping entries

[dandye]

Thank you for adding these case management tools to the SOAR MCP server. This is a very valuable addition to the repository.

Before we can merge this PR, please address the following feedback items:

1. Add explicit = None defaults to optional parameter signatures:
   In create_case (lines 30-61) and close_case (lines 142-148), optional parameters declare Field(default=None, ...) inside Annotated, but omit = None on the parameter declaration itself.

   Please add = None to the parameter signatures so standard Python inspection recognizes them as optional defaults:

   # In create_case:
   priority: Annotated[Optional[str], Field(default=None, description="...")] = None,
   description: Annotated[Optional[str], Field(default=None, description="...")] = None,
   environment: Annotated[Optional[str], Field(default=None, description="...")] = None,
   
   # In close_case:
   tags: Annotated[Optional[str], Field(default=None, description="...")] = None,

2. Add json_schema_extra enum constraint for reason in close_case:
   The docstring specifies that reason must be one of Malicious, NotMalicious, Maintenance, Inconclusive. To ensure LLM callers adhere to valid enum literals without hallucinating arbitrary strings, please add the enum schema constraint (similar to priority in create_case / change_case_priority):

   reason: Annotated[
       str,
       Field(
           ...,
           description="The close reason category for the case.",
           json_schema_extra={
               "enum": [
                   "Malicious",
                   "NotMalicious",
                   "Maintenance",
                   "Inconclusive",
               ]
           },
       ),
   ],

3. Add unit tests:
   Please add unit tests covering the new tools in tests/ verifying that each tool function constructs the correct request payload and invokes the intended endpoint on http_client.

Once these updates are in place, we will be happy to merge this PR.