Add MAX_STEAMID_LENGTH

[sirdigbot]

I feel like this is sorely missing since I've had to define it in so many plugins I've written.

The maximum theoretical size of a 'valid' SteamID (according to the valve wiki) is 23 bytes including null STEAM_255:1:2147483647.

The only exception that I know of is STEAM_ID_STOP_IGNORING_RETVALS which is 31* bytes including null.

In the interest of keeping that error value meaningful, either:

• It should be changed to fit within 23 bytes, which could potentially break something for no reason.
• There should be only 1 constant for the size of a SteamID that not only fits every type of ID but also the error message.

[sirdigbot]

* - I didn't realise the size was off by 1 until I already hit submit, but I'm not sure if it should be changed

[KyleSanderson]

@asherkin I remember you had reservations about hard coding steam authentication eons ago (which we well moved on from, which was also well before steam|/3). Based on the trajectory I'm OK with this. Fun/base have this at 64 chars right now on a [3][64] array. Long term to avoid the MAXPLAYERS+2 issue I think we want to reserve a 128b rendered value. WDYT?

[asherkin]

👍 32 seems like a good length to me.

[asherkin]

That said, I think this should be MAX_AUTHID_LENGTH - the SM API doesn't use "SteamID" at the top-level.

[asherkin]

It turns out that Valve actually have this defined in the SDK

#define      MAX_NETWORKID_LENGTH            64  // num chars for a network (i.e steam) ID