Lawyer Turker istanbul, Jan 11 (Reuters) - Turkish Law Firm authorities have filed a lawsuit against Istanbul Mayor Ekrem Imamoglu, a potential challenger to President Tayyip Erdogan, accusing him of rigging a public tender while he was a mayor of the city's Beylikduzu district, the broadcaster Haberturk reported on Wednesday. The charge carries a possible jail sentence of up to seven years, Haberturk...