A trigger that show the user that has made an insertion I have the following code

create table o_c(
op_id NUMBER(10,0) PRIMARY KEY NOT NULL,
n_c VARCHAR2(50) NOT NULL,
op VARCHAR2(500) NOT NULL,
amount NUMBER(9,2)
);

create table a_o(
a_id NUMBER(10,0) PRIMARY KEY NOT NULL,
details VARCHAR2(500) NOT NULL
);

create sequence a_o_seq
START WITH     1
INCREMENT BY   1
NOCACHE
NOCYCLE;


And I need a trigger that writes in "details" of each record this message:

User username performed an insert operation. The data added were saved with op_id = value, the operation was performed on the date DATE
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