feat(spanner): implement search_catalog tool and add docs/tests

[anikasharma03]

Description

• Implements search tool for Spanner assets using Dataplex.
• Updates Spanner source to handle Dataplex clients with caching and OAuth.
• Adds prebuilt tool configurations for both GoogleSQL and PostgreSQL dialects.
• Includes tests and documentation.

PR Checklist

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🛠️ Fixes #<issue_number_goes_here>

[gemini-code-assist]

Code Review

This pull request introduces the search_catalog tool for Cloud Spanner, enabling searches for data assets in Knowledge Catalog (Dataplex). The changes include the tool implementation, documentation, and updates to the Spanner source to support Dataplex client initialization with OAuth token caching. Review feedback highlights a style guide violation in the documentation title format, suggests improving the ExtractType logic for better LLM context, and identifies a redundant nil check on the search iterator.

[gemini-code-assist]

According to the repository rules, the title in the YAML frontmatter for tool documentation files should use kebab-case for the tool name, followed by ' Tool'.

Suggested change

	title: "spanner-search-catalog"
	title: "spanner-search-catalog Tool"

References

1. For tool documentation files, the title in the YAML frontmatter should use kebab-case for the tool name, followed by ' Tool'.

[gemini-code-assist]

The ExtractType function returns an empty string if the entry type suffix is not found in the typeMap. This might be confusing for the LLM. It would be better to return the original suffix or a default value like 'UNKNOWN' when a mapping is missing.

func ExtractType(resourceString string) string {
	lastIndex := strings.LastIndex(resourceString, "/")
	if lastIndex == -1 {
		return resourceString
	}
	suffix := resourceString[lastIndex+1:]
	if val, ok := typeMap[suffix]; ok {
		return val
	}
	return suffix
}

[gemini-code-assist]

The SearchEntries method in the generated Dataplex client returns an iterator and does not return nil. This check is redundant. Errors should be handled during iteration using it.Next().

it := catalogClient.SearchEntries(ctx, req)

[TanmayVartak]

Thanks for adding this functionality to Spanner source.

[TanmayVartak]

Can GetCatalogClient be part of utils shared across multiple data sources? Code is generic and nothing specific to Spanner.

[TanmayVartak]

Fix formatting.

[TanmayVartak]

Apart from typeMap everything in this function is generic and may provide additional opportunity to move generic functionality under util. Consider base class "SearchCatalog(typeMap, )"