Don't allow duplicate relays

[dmnyc]

Users should not be able to add the same relay twice.

Sometimes they will add them with minor syntax differences, such as:

wss://nos.lol
and
wss://nos.lol/

Damus should detect when a user is adding a relay they already have set and reject it.

[alltheseas]

I think this is a duplicate. @jb55 I dont think we have pushed out the trailing slash duplicate relay check yet, correct?

#1766 (comment)

[jb55]

On Sat, Jan 13, 2024 at 08:49:20AM -0800, alltheseas wrote: I think this is a duplicate. @jb55 I dont think we have pushed out the trailing slash duplicate relay check yet, correct?

I think there was work done at a surface level but there's multiple areas where this is a problem. We just need to fix it by having this duplicate checking and filtering logic all in one place.

[alltheseas]

@mleku feedback:

a rule of URLs: sanitize them

like all user input, you can't trust it

make it into canonical form for the specific use never ever use any value from outside your code without making it clean and canonical

sql injections only worked because of lack of this processing

[alltheseas]

fixed 1.9 testflight