add parameters too all requests

DefaultParamserializer.h

#import "AFURLRequestSerialization.h"

@interface DefaultParamsSerializer : AFHTTPRequestSerializer

@end

DefaultParamsSerializer.m

#import "DefaultParamsSerializer.h"

@implementation DefaultParamsSerializer

- (NSMutableURLRequest *)requestWithMethod:(NSString *)method URLString:(NSString *)URLString parameters:(id)parameters error:(NSError *__autoreleasing *)error
{
    if (parameters) {
        if ([parameters isKindOfClass:[NSDictionary class]]) {
            NSMutableDictionary *mParams = [parameters mutableCopy];
            mParams[@"key"] = @"value";
            parameters = [mParams copy];
        }
    } else {
        parameters = @{@"key": @"value"};
    }
    return [super requestWithMethod:method URLString:URLString parameters:parameters error:error];
}

// override these too if you use them
//- (NSMutableURLRequest *)multipartFormRequestWithMethod:(NSString *)method URLString:(NSString *)URLString parameters:(NSDictionary *)parameters constructingBodyWithBlock:(void (^)(id<AFMultipartFormData>))block error:(NSError **)error
//- (NSURLRequest *)requestBySerializingRequest:(NSURLRequest *)request withParameters:(id)parameters error:(NSError **)error

@end