feat(rql): add function to get data type of field

[whoAbhishekSah]

Description

This PR introduces a new utility function GetDataTypeOfField that allows runtime validation and retrieval of field data types from RQL struct tags. This enables better type safety and validation when building queries or processing data.

New Function

func GetDataTypeOfField(fieldName string, checkStruct interface{}) (string, error)

The function:

• Takes a field name and struct instance as input
• Returns the RQL data type ("string", "number", "bool", "datetime") for the field
• Defaults to "string" type if no type is explicitly specified
• Returns error for invalid fields or unsupported data types

Usage Example

type User struct {
    Name      string    `rql:"name=full_name,type=string"`
    Age       int       `rql:"name=age,type=number"`
    IsActive  bool      `rql:"name=active,type=bool"`
    JoinDate  time.Time `rql:"name=joined_at,type=datetime"`
    Notes     string    `rql:"name=notes"` // defaults to string type
}

user := User{}
dataType, err := GetDataTypeOfField("age", user)
// Returns "number", nil

dataType, err := GetDataTypeOfField("invalid_field", user)
// Returns "", error("'invalid_field' is not a valid field")

Features

• Supports all RQL data types: string, number, bool, datetime
• Works with both struct field names and custom names defined in tags
• Case-insensitive field name matching
• Graceful fallback to string type when no type is specified
• Clear error messages for invalid cases

Test Coverage

Added comprehensive test suite covering:

• All supported data types
• Custom field name lookups
• Default type handling
• Error scenarios
• Edge cases

Benefits

• Enables runtime type validation for RQL queries
• Helps prevent type-related errors early in the query building process
• Simplifies implementation of type-aware query builders and validators