Fix HTTP error handling in payjoin-cli

[spacebear21]

While testing @Arowolokehinde 's PR #1498 I noticed that cli was attempting to process the OHTTP response even though it was returning a 403. This fix ensures we actually bubble up HTTP error responses from the ohttp relay:

Before:

❯ cargo run -- send $BIP21 --fee-rate 1
   Compiling payjoin-cli v0.2.0 (/Users/spacebear/Projects/rust-payjoin/payjoin-cli)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 1.63s
     Running `/Users/spacebear/Projects/rust-payjoin/target/debug/payjoin-cli send 'bitcoin:bcrt1qpvnwwzs00tjys006szgx26krf8kewmk8qah2ah?amount=0.00001&pjos=0&pj=HTTPS://PAYJO.IN/8EZPMVL7YVTHZ%23EX1C4PW56G-OH1QYPFLM8XL59R0XV4VGPLS7FRDSSM4TUXL07TXCWC4S0GLVLNK2SE4NQ-RK1QDN0WY7AAH7YLXKJYHEN7SSDT04WG2JKMDY3UGGGWDU8S6X9GXSZG' --fee-rate 1`
Bootstrapping private network transport over Oblivious HTTP
Error: Transient error: Directory response error: Unexpected response size 0, expected 8192 bytes

After:

❯ cargo run -- send $BIP21 --fee-rate 1
   Compiling payjoin-cli v0.2.0 (/Users/spacebear/Projects/rust-payjoin/payjoin-cli)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 1.89s
     Running `/Users/spacebear/Projects/rust-payjoin/target/debug/payjoin-cli send 'bitcoin:bcrt1qpvnwwzs00tjys006szgx26krf8kewmk8qah2ah?amount=0.00001&pjos=0&pj=HTTPS://PAYJO.IN/8EZPMVL7YVTHZ%23EX1C4PW56G-OH1QYPFLM8XL59R0XV4VGPLS7FRDSSM4TUXL07TXCWC4S0GLVLNK2SE4NQ-RK1QDN0WY7AAH7YLXKJYHEN7SSDT04WG2JKMDY3UGGGWDU8S6X9GXSZG' --fee-rate 1`
Bootstrapping private network transport over Oblivious HTTP
Error: HTTP request failed

Caused by:
    HTTP status client error (403 Forbidden) for url (https://payjo.in/https://payjo.in/)

Closes #1394

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[coveralls]

Coverage Report for CI Build 24789507463

Coverage increased (+0.03%) to 84.953%

Details

• Coverage increased (+0.03%) from the base build.
• Patch coverage: 2 of 2 lines across 1 file are fully covered (100%).
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	13371
Covered Lines:	11359
Line Coverage:	84.95%
Coverage Strength:	400.76 hits per line

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💛 - Coveralls

[arminsabouri]

utACK 79da53c