feat: implement use the '-' mark to ignore writing values for field

[daviderli614]

What's changed and what's your intention?

Similar to the following struct, The CPU field is marked with -, will write the zero value of the type:

type Monitor struct {
	ID          int64     `greptime:"tag;column:id;type:int64"`
	Host        string    `greptime:"tag;column:host;type:string"`
	Memory      uint64    `greptime:"field;column:memory;type:uint64"`
	Cpu         float64   `greptime:"-"`
	Temperature int64     `greptime:"field;column:temperature;type:int64"`
	Running     bool      `greptime:"field;column:running;type:boolean"`
	Ts          time.Time `greptime:"timestamp;column:ts;type:timestamp;precision:millisecond"`
}

Result:

+------+-----------+--------+------+-------------+---------+----------------------------+
| id   | host      | memory | cpu  | temperature | running | ts                         |
+------+-----------+--------+------+-------------+---------+----------------------------+
|    0 | 127.0.0.1 |      1 |    0 |          -1 |       0 | 2024-12-02 07:31:46.403000 |
|    0 | 127.0.0.1 |      1 |    0 |          -1 |       0 | 2024-12-02 07:31:46.587000 |
|    1 | 127.0.0.2 |      1 |    0 |          -1 |       1 | 2024-12-02 07:31:46.403000 |
|    1 | 127.0.0.2 |      1 |    0 |          -1 |       1 | 2024-12-02 07:31:46.587000 |
|    2 | 127.0.0.3 |      2 |    0 |          -2 |       1 | 2024-12-02 07:31:46.403000 |
|    2 | 127.0.0.3 |      2 |    0 |          -2 |       1 | 2024-12-02 07:31:46.587000 |
+------+-----------+--------+------+-------------+---------+----------------------------+
6 rows in set (0.03 sec)

Checklist

• I have added the necessary unit tests and integration tests.

Refer to a related PR or issue link (optional)

#54

[zyy17]

IMO, the meaning of greptime:"-" should be: ignore this field when writing and read with struct.

For this PR, it just writes the zero value, it's not a field ignore.

[daviderli614]

IMO, the meaning of greptime:"-" should be: ignore this field when writing and read with struct.

For this PR, it just writes the zero value, it's not a field ignore.

Wait for me to modify it soon.

[daviderli614]

Make some changes, please review again. @zyy17
Usage Examples: README
There a unit test TestParseSchemaWithSkipFields has passed.

[zyy17]

LGTM