Add support for byte[] to String/FixedString types

[MaceWindu]

ClickHouse String/FixedString types store binary data, but provider supports only UTF8 string representation.

It doesn't work well in some cases:

• use of `byte[]' results in "System.Byte[]" value in database (here)
• not all binary data represents valid utf8 sequence and doesn't survive conversion to string as UTF8 and back without data loss. E.g. 0xFF will be 0xEF 0xBF 0xBD after binary->string->binary conversion

[DarkWanderer]

I understand the desire to use string values as storage for byte arrays, but it is not possible to resolve without introducing ambiguity which cannot be resolved at driver level. Specifically, even if I write the value as a byte array to database, I will not be able to read it back as it's not possible to understand whether the value is a valid string or a byte array in general case

Can you use Array(UInt8) in ClickHouse instead? See #110

[MaceWindu]

Well, actually this is not an issue for me - I don't use ClickHouse.

I'm just implementing support for it in linq2db and report back issues, discovered during testing process.

Currently I'm working with 3 providers:

• your provider
• Octonica binary provider
• mysql interface provider

and binary support present only in Octonica:

• in data reader they allow to get raw data if you call GetFieldValue<byte[]> and utf-8 string for GetString call (your provider currently doesn't implement GetFieldValue)
• in bulk copy they allow to specify used Type for column: string or byte[] (which I find unnecessary as both types should be already recognized as valid values, but that's not really important).
• as for query parameters - I don't use them for ClickHouse, so I have nothing to add here

MySql interface also has issues with binary data reads, but this is due incorrect implementation on server side.

[DarkWanderer]

What is the scenario you use/plan to use this in linq2db for?